JPH0427247B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to monocomponent isocyanate capped prepolymer compositions which are stable at room temperature. The isocyanate-capped prepolymers of this invention are useful as adhesives and can be cured (chain-extended or cross-linked) by slight heating. Furthermore, the one-part polyurethane of the present invention has a long pot life at room temperature and can be cured by slight heating either directly or via the substrate to which it is applied. Furthermore, the present invention provides a method for producing a thermosetting, one-component isocyanate capped prepolymer and a method for using the same, such as a method for forming a cured film, a method for adhering substrates to each other, etc. It is something. BACKGROUND OF THE INVENTION Polyurethane chemistry is still evolving since its basic prepolymer and polymer formation, modification, and curing principles were discovered decades ago. Polyurethane was first used as a foam, but non-cellular elastomers were developed in the early 1950s. Also contributing to the development of polyurethane was the discovery of more effective catalysts. For example, the discovery of organometallic compounds that significantly accelerate the reaction between hydroxyl and isocyanate groups. Like other elastomers, polyurethane elastomers can be used as adhesives, coatings, and sealants. Even in the technical field of polyurethane, it is convenient to use a prepolymer system that can be further cured into a polymer. A typical prepolymer is formed by a chain consisting of repeating units having less than one unreacted isocyanate group. This prepolymer can be reacted with crosslinkers or chain extenders to at least double the molecular weight, and in some cases significantly increase the molecular weight. The crosslinker or chain extender itself also has repeating units. This may be a polyfunctional monomer. Monofunctional reactants are believed to provide chain termination rather than chain extension or crosslinking. A very commonly used chain extension or crosslinking monomer is water or steam. Some types of crosslinking are effected by forming biuret bonds through water/NCO reactions. Many so-called one-part curable polyurethanes are actually steam curable. However, they are in a sense two-component. That is, there is no second component of the polyurethane or polyurea forming system present in the prepolymer composition, but when the first part is coated onto a substrate or comes into contact with vapor in the ambient air, the second part ingredients will be supplied. Therefore, there are few one-component curable polyurethane systems that inherently have a second component potentially incorporated therein. It is theoretically possible to make a two-part curable polymer-forming system into a one-part system by potentially incorporating the second component into the first component under normal conditions. In this case, heating is a common means of activating this latent reactant. This method is particularly advantageous for epoxy systems. This is because a temperature range in which the epoxide or oxirane ring is relatively inactive can be easily selected. This thermal curing method is more difficult in the case of polyurethane or polyisocyanate systems due to the high reactivity of the -NCO group even at relatively low temperatures. Especially for aromatic isocyanates (i.e. -
When the NCO group is directly substituted on the aromatic ring), the reactivity is significant, and less so in the case of aliphatic and cycloaliphatic polyisocyanates. In addition, in the case of xylylene-type isocyanate, regarding reactivity,
It is located between these two. -Even if the NCO groups have little chance of reacting with active hydrogen-containing reactants at room temperature, the presence of catalysts such as tertiary amines, organometallic compounds, etc. can reduce multifunctional chains in one-component thermosetting prepolymers. This makes it more difficult to form compositions that incorporate extension or crosslinking agents. Organometallic catalysts accelerate polyol-polyisocyanate reactions at room temperature. When the polyhydric alcohol is contacted with the polyisocyanate at room temperature in the presence of the organometallic catalyst, the system is considered to no longer have latent curing properties. moreover,
This system is believed to increase in viscosity over time and rapidly gel within a few hours. Common means to prevent gelation during storage are removable monofunctional capping agents,
For example, the end of the prepolymer with phenol
This is a method of blocking NCO groups. Phenol easily reacts with isocyanate groups to form urethane bonds (-NH-CO-O-), but this reaction is reversible at relatively low temperatures. However, this unblocking step results in cumbersome development. The heat generation pattern during the curing process of polyurethane systems is complex, often at least two
Two exothermic peaks are displayed. Note that once the unblocking of the prepolymer occurs, free −NCO
The reaction between and free hydroxyl groups is exothermic. If blocking of the -NCO with a phenol or other thermoremovable capping agent is not performed, polyethers, ester-modified polyether polyols, isocyanate-containing prepolymers, organometallic catalysts, polyhydroxyl-crosslinked single chain extension compounds ( For example, glycerin, pentaerythritol) are believed to provide rapid hardening elastomers (U.S. Pat.
(See No. 3725355). However, solid monomeric polyols can be incorporated into one-component prepolymer systems under certain conditions to obtain relatively slow or stable mixtures (see US Pat. No. 3,488,302). The stable mixtures of isocyanate prepolymers and solid polyols described in this patent are useful as caulks or sealants and are applied in ribbon form or as paints. These mixtures are firmly adhered to the surface to be adhered by heating and curing. The curing temperature in this heat curing step is said to be lower than the melting point of the polyol in the mixture. The object of this invention is to provide a one-component isocyanate capped prepolymer composition with good storage stability. The prepolymers according to the invention can be prepared from aliphatic or cycloaliphatic isocyanate capped prepolymers and monomeric, dimeric or trimeric polyols of the pentaerythritol type. The prepolymer composition is stable at room temperature and pressure for at least about 48 hours, and generally for weeks to months. This prepolymer can be cured at temperatures above 60°C, preferably above 85°C. Further, this curing temperature is preferably lower than the melting point of the pentaerythritol type polyol. As used herein, curing refers to a chain extension or crosslinking reaction between the free hydroxyl groups of the pentaerythritol-type polyol and the free -NCO of the isocyanate-capped prepolymer, thereby at least doubling the molecular weight of the prepolymer. death,
Furthermore, a significant increase in molecular weight generally results in the formation of a foamy solid polymer or resin. That is, the one-component composition according to the present invention (a) is fluid at 60°C or higher and has a molecular weight of 250 or higher;
having a chain of repeating units selected from oxyalkylene, ester and mixtures thereof,
an aliphatic or alicyclic isocyanate capped prepolymer forming a uniformly dispersed continuous phase; (b) a solid finely divided polyol having the structural formula: (ROCH ₂ ) ₃ C−[CH _{2 2C} ( _CH2OR ) ₂
] _-o CH ₂ OR (wherein R is hydrogen or an aliphatic, alicyclic, or aromatic group, two or more of R is hydrogen, n is an integer from 0 to 2) Also, this polyol is at least partially incompatible with the prepolymer at temperatures below 60°C; and (c) an organometallic or metal salt catalyst that promotes the reaction between isocyanate groups and the free hydroxyl groups of (b) above; Dispersed in a continuous phase; Preferred polyisocyanate capping agents are those with unequal reactivity --NCO substitutions. For example, isophorone diisocyanate (IPDI). Preferred polymer polyols capped with diisocyanates include polyester diols, triols,
Tetrols, particularly triols, are preferred. The prepolymers of this invention are made by capping a polymeric polyol with an aliphatic or cycloaliphatic polyisocyanate. In this case
NCO/OH ratio is (0.8-3):1, preferably 2:
1, thereby making it possible to obtain isocyanate-capped prepolymers that are fluid or extrudable at room temperature. The monomeric, dimeric or trimeric polyol is uniformly dispersed in the continuous phase containing the prepolymer. Since this dispersed or suspended phase is a solid, it is introduced in finely divided form;
Preferably, a mixture with a plasticizer that is inert to hydroxyl groups and isocyanate groups is used. The water-binder may be added to the plasticizer. The prepolymer composition of the present invention is applied to a substrate,
Cure by heating. This prepolymer (preferably very low in solvent and almost 100% solids) is used to bond substrates together due to its high adhesive strength. The viscosity of this prepolymer composition may be adjusted using a thickener or a thixotropic agent. The addition of a thickener gives the composition stiffness so that it is possible to use a caulking or adhesive handling gun to push the composition through small openings, forming the adhesive into ribbon images or beads. can be done. In addition, in this specification, "active hydrogen" is defined by J. Amer.
Chem.Soc.49:3181 (1927)
According to the definition by Zerewitinoff test. An example of this active hydrogen atom is hydrogen in the hydroxyl group of a monohydric or polyhydric alcohol. Although such active hydrogen is particularly preferred in the present invention, it is known that other active hydrogens are contained in mercaptans, amines, acids, and the like. "Aliphatic polyisocyanates" include all polyisocyanates in which at least one -NCO group is bonded to an alicycloaliphatic group. Preferred aliphatic polyisocyanates are non-aromatic, ie, those in which -NCO groups are not bonded to aromatic rings. However, an aliphatic polyisocyanate in which -NCO is bonded to an alicyclic group is suitable and preferred. "Alicyclic polyisocyanate" includes all polyisocyanates in which at least one -NCO is bonded directly to an alicyclic group. Note that, as mentioned above, this is a non-aromatic compound. "IPDI" means isophorone diisocyanate or 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexyl isocyanate. "% Solids" is an expression commonly used in the paint chemistry and polyester resin coating fields.
This term refers to the amount of material (whether solid or liquid) remaining after removal of volatile materials or materials not involved in curing the composition.
Thus, for example, 85% prepolymer, 5%
A polyurethane prepolymer composition consisting of pigment, 10% organic solvent can be referred to as a "90% solids" composition. Common plasticizers are well within the category of "solids" as opposed to solvents. The reason is that it is substantially non-volatile. It is further believed that the plasticizer forms part of the solid elastomer or resin formed by curing the prepolymer with the solid polyol phase. By "uniformly dispersed" is meant a discontinuous phase dispersed or suspended throughout the continuous phase. In addition, the degree of suspension or dispersion and the degree of uniformity mean a degree at which sedimentation does not substantially occur under normal conditions. The present invention consists of a combination of a continuous phase of terminal isocyanate prepolymer and a second phase of solid particulate polyol curing agent as described above. This second phase is not readily soluble in the continuous phase, but is uniformly dispersed within it and comes into intimate contact with the prepolymer. When this is heated to above 60°C, preferably at least 85°C, the curing reaction is initiated and proceeds exothermically until completion, at which time a solid polyurethane polymer or resin is obtained. By changing the NCO/OH ratio, the functionality of the starting material and the properties of the final polyurethane prepolymer are also changed. For example, when the NCO/OH ratio is large, a large range of adhesive properties is obtained.
When the NCO/OH ratio is less than 1:1, a product with a large proportion of terminal hydroxyl groups and a relatively low molecular weight can be obtained. As the NCO/OH ratio approaches 1:1, the degree of linear chain extension increases and thermoplastic properties occur, and by appropriate selection of the polymerization partner, elastomeric properties appear. The one-component curable polyurethane composition according to the present invention can be cured into a highly crosslinked adhesive or an elastomer composition with a low crosslink density. The highly crosslinked cured polyurethane according to the invention can be plasticized. The uncured one-part polyurethane prepolymer can be mixed with plasticizers and other modifiers that do not react with isocyanates or hydroxyl groups. Preferably, the plasticizer is substantially inert towards these groups. Similarly,
If viscosity modifiers are added, it is generally preferred that these components be inert to NCO/OH reactions. This plasticizer can also have a viscosity adjusting effect and is preferably insoluble in water in actual use. high boiling hydrocarbons,
For example, hydrogenated polynuclear aromatics are particularly preferred as plasticizers. In order to impart thickening or thixotropic properties to one-component polyurethane for use as caulking, sealants, anti-sag coatings, adhesives, etc., known organic and inorganic thickeners or thixotropic agents are added to improve the viscosity. Or the shear-dependent viscosity can also be increased. It is not easy to find organic thickeners and thixotropic agents that are inert towards isocyanates and hydroxyl groups. Even inorganic thickeners and thixotropic agents have isocyanate-reactive groups such as silanol (SiOH). Methods of masking cyanol groups on silicates such as particulate silica and hydrated magnesium aluminum silicate are also known. For example, treating a silica or silicate powder with silicone or a reactive silicon-containing monomer or other hydroxide-reactive or cyanol-compatible compound to remove or significantly reduce the availability of cyanol groups on the surface of the silica or silicate powder. be able to. Despite such treatment, the silica or silicate particles can retain a significant thickening or thixotropic effect. The particle size of these inorganic agents is generally in the colloid-forming range, generally from 1 nanometer to 1 micron. These colloidal particles tend to form agglomerates and to form porosity with a large surface area. Silicone-modified hydrophobic silica is useful as a toughening agent for the one-part polyurethane compositions of the present invention. Note that "silicone" has the same meaning as organopolysiloxane polymer. The terminal isocyanate polyurethane prepolymers according to the invention can be obtained from polymer polyols and aliphatic or cycloaliphatic polyisocyanates. [Polymer polyol] The polymer polyol is fluid at room temperature and has a molecular weight of 250 or more, generally 500 or more.
The chain of oxyalkylene or ester repeat units has an influence on the molecular weight. Polymer polyols are composed of linear or side chains of repeating units having hydroxyl groups at their ends. Simply put, these hydroxyl groups are the only active hydrogen-containing substituents in the polyol structure. Polyester and polyether polyols have molecular weights in the hundreds of thousands or millions and are commercially available. However, the viscosity of the resulting prepolymer system will be less than 20,000 molecular weight, more typically less than 5,000 or 10,000, and even more preferably less than 500.
controllable by synthesis from ~3000 polymer polyols. The functionality of the polymeric polyol can be varied over a wide range by appropriate selection of the monomeric polyol core or other active hydrogen-containing core containing the desired number of active hydrogens or active hydrogen-containing substituents. For example, polymeric polyols with three functional groups can be grown from glycerin, trimethylolpropane, triethanolamine, monomeric triol initiators or cores.
(If desired, the functionality may be only 2 and water, glycols, etc. may be used as the initiator or nucleus). For polymeric polyols with functionality of 4, ethylene diamine and other di-primary amines may be used. The two active hydrogens on each amine substituent have substantially equal reactivity. Sucrose salts or carbohydrates having similar units or derivatives thereof may be used as initiators with very high functionality, for example up to about 8. A hydroxide-containing oil (such as vegetable oil) may be used as a highly functional polyol. After the polyol reacts with the polyisocyanate, the resulting prepolymer has 1
Above, it will have an additional 3 or 4, or even 6, but generally up to 9 isocyanate groups. Preferred polyoxyalkylene or polyester containing polyols are usually diols, triols or tetrols. The equivalent weight of these polymer polyols is generally 125-2500 and 200-1000
appears to be the most preferred adhesive system. Polyester polyols having a functionality of 2 or more are particularly effective as adhesives. Poly(epsilon-caprolactone) polyols of various functionalities and equivalent weights are readily available and suitable. Among commercially available polyols, “NIAX polyol”
PCP” has a melting point of 60°C or lower, and is generally 40°C.
It is as follows. The average number of hydroxyl groups in this polyol is
It ranges from 37 to 560. Therefore, the equivalent is approximately
There are 1520 large ones to 100 small ones.
Furthermore, the average molecular weight of this polyol is 300 to 3000
It is said that These polyols do not all have the same effect, but their average molecular weight is
Most preferably, the number of hydroxyl groups is 500 or more and the average number of hydroxyl groups is about 450 or less. [Polyisocyanate-Capping Agent] The above polymer polyol is capped with a polyisocyanate to form a terminal isocyanate polyurethane polymer. In order to obtain a one-component curable polyurethane prepolymer system that is stable at room temperature, the capping agent used is an aliphatic or cycloaliphatic polyisocyanate, particularly one having a functionality of 2 or more and 4 or less. Aliphatic and cycloaliphatic di- and triisocyanates are commercially available, the most common being alkylene diisocyanates, IPDI,
Hydrogenated aromatic and xylylethyl diisocyanates. Since, as mentioned above, non-aromatic polyisocyanates are preferred, the aromatic rings initially present in the starting materials must be partially or fully hydrogenated. However, polynuclear polyisocyanates can also be selectively hydrogenated, so that one ring is alicyclic and the other ring remains aromatic. Because the aromatic/cycloaliphatic diisocyanate reacts more readily with hydroxyl groups at its aromatic end, a terminal isocyanate prepolymer is formed in which the free -NCO groups are almost entirely attached to the cycloaliphatic end of the capping agent. As a result, it is believed that a prepolymer is obtained which has the properties of an alicyclic isocyanate capped material that does not substantially have the properties of aromatic isocyanates. The reaction theory governing the formation of this prepolymer also indicates that such a result would occur. However, totally non-aromatic polyisocyanates are generally the preferred capping agents because of the statistical probability of free aromatic isocyanates. The non-aromatic polyisocyanate does not necessarily have a symmetrical structure or an -NCO group with equivalent reactivity. For example, the -NCO groups in IPDI, which is considered preferred, do not all have the same reactivity. One of the -NCOs is directly bonded to the alicyclic ring, and the other is "insulated" by a methylene group. It is assumed that the polyurethane prepolymer used in the present invention generally has two less reactive --NCO groups in the IPDI molecule at the ends. That is, this appears to be due to the kinetics governing the formation of this prepolymer. It is believed that these relatively less reactive terminal isocyanate groups contribute to a significant improvement in the room temperature stability of one-part curable polyurethane systems. Theoretically speaking, another factor contributing to this room temperature stability is due to the incompatibility of the solid pentaerythritol-type curing agent, which is uniformly dispersed within the uncured prepolymer of this one-component system. I think that the. This incompatibility decreases considerably above 60°C, especially above 85°C, and becomes increasingly homogeneous, leading to a system in which the slow-reacting free-NCO of IPDI rapidly reacts with the curing agent. . As a result, a curing reaction with a single exothermic peak is formed. In the capping step to form the curable prepolymer, the NCO/OH ratio can be varied, depending on the desired properties of the polymer. If you expect the cured polymer to have high chain extension or elastomeric properties,
An NCO/OH ratio of 0.8 to 1.2 is most effective.
If a certain degree of elasticity, impact resistance and stress relaxation properties are to be obtained in the coating composition, the NCO/OH ratio should be fairly high, for example 2:1. Higher NCO/OH ratios are preferred for adhesives, generally 2:1 or higher. In the present invention, it seems that no advantage can be found by setting this ratio to 3:1 or more. Products with appropriate stiffness, adhesive strength, and stress relaxation properties have a low NCO/OH ratio.
Obtained when the ratio is 2.8:1 or less. The curing agent is a polyhydric alcohol and is therefore effective in lowering the overall NCO/OH ratio.
For example, by adding a hardening agent, the overall
The NCO/OH ratio can be reduced by 10-75%. When the NCO/OH ratio during uncured prepolymer formation is greater than 1.5 (e.g. 2:1 to 3:1)
By adding a hardening agent, this can be reduced to 1.5 or less. But again, this ratio is about 0.8
It is preferable to set it as above. In the adhesive system according to the invention, it is preferred that the NCO/OH ratio be 1:1 or higher (even after addition of the curing agent). [Curing Agent] The monomeric or substantially monomeric polyhydric alcohol used as a curing agent in the dispersed or suspended phase of the one-component curable polyurethane system of the present invention is a solid with a melting point above the appropriate curing temperature. It is. This curing temperature is generally below 250<0>C, more generally between 85 and 200<0>C. For example, so-called "spot weld" cures are generally performed at 150-190°C for several minutes (eg, 0.5-10 minutes). Of course, this cure temperature is related to time. Conventional in-furnace curing is performed at lower temperatures for longer periods of time.
As mentioned above, curing does not substantially proceed at temperatures below 60°C or even at 85°C. Pentaerythritol is a preferred polyhydric alcohol curing agent in the present invention. The melting point of this substance is said to be 260°C or 262°C. This has poor compatibility with uncured polyurethane prepolymers and is therefore preferred for the present invention. The hydroxyl group of pentaerythritol shows no reactivity with the -NCO group of the IPDI residue at room temperature and normal pressure, and this is the same even in the presence of an organometallic compound catalyst. Esterification of pentaerythritol, especially with lower aliphatic acyl groups, considerably reduces the melting point of the resulting ester. Therefore, such esterification is generally undesirable. moreover,
At least two hydroxyl groups of pentaerythritol (or its dimer or trimer) must remain in order to react with the -NCO group during the curing reaction. Pentaerythritol 2
Non-esterified versions of the mer and trimer are useful.
This is because the corresponding industrial pentaerythritol contains a considerable amount of such non-esterified products. In particular, the dimer appears to behave similarly to pentaerythritol itself.
(The dimer, or dipentaerythritol, is present in greater quantities in industrial pentaerythritol than the trimer, or tripentaerythritol.) For these reasons, this pentaerythritol does not require purity higher than industrial use. Note that highly purified pentaerythritol is also commercially available and is often used in the production of explosive pentaerythritol tetranitrate. In the present invention, when pentaerythritol ester or its dimer or trimer ester is used as a curing agent, up to two of the pentaerythritol methylol groups are -CH ₂ OR (where R is an aliphatic or alicyclic group). Alternatively, it can be converted into an aromatic acyl group, preferably a group that does not lower the melting point of the resulting ester below 150°C. In the case of a dimer,
Up to four methylol groups can be converted to ester groups without reducing the number of hydroxyl groups below two. Also for trimers this number is increased to 6. However, even if the degree of esterification is increased, it is not particularly advantageous. In addition, this trimer is
It is not as easily available as the dimer, and is still difficult to obtain compared to pentaerythritol. Pentaerythritol can be produced relatively easily, for example, by aldol condensation/chromium-cannizaro reaction between acetaldehyde and thymol formaldehyde. Dipentaerythritol is obtained as a by-product in this reaction and trimer is not obtained in this method. [Curing Catalyst] In order to make the one-component curable polyurethane composition according to the present invention more satisfactory, it is preferable to include a reaction catalyst between the isocyanate group and the free hydroxyl group of the curing agent. As is known, many organometallic compounds and metal salts are available that can promote the NCO/OH reaction. It has been discovered that organomercury catalysts can selectively promote NCO/polyol reactions even in the presence of other active hydrogen-containing compounds such as water. Organometallic and metal salt catalysts used in polyurethane chemistry include metals or metal ions of groups -B, -B and -A, such as lead, tin, iron, mercury, and the like. Bismuth, titanium, antimony, uranium, cadmium, cobalt, thorium, aluminum, zinc, nickel,
Organometallic compounds of molybdenum, vanadium, copper, manganese, and zirconium are also known to be effective catalysts (see US Pat. No. 3,691,135). The use of organotins is particularly common. for example
_{R 2 So _} R _{3 So} X catalysts are also known (see US Pat. No. 3,351,573). mercury salt,
For example, mercury acetate is also known as an NCO/OH reaction catalyst. These salts have low catalytic activity and may require the addition of moral weight (gram molecules). The compound RHgX (where R is an aliphatic, aromatic or alicyclic group, and X is OCOR'(R' is the same as R above)) has a strong catalytic effect and is one of the preferred organometallic catalysts. Effective amounts of organomercury compounds range from 0.1 to 1% by weight of the one-part curable polyurethane system. The same is true for organic tin compounds. Adding more than necessary is not particularly advantageous. However, in the case of a metal salt having no direct bond between carbon and metal, it can be advantageous to add it in a large amount compared to the case of an organic metal. [Other components] Known fillers, extenders, pigments, etc. can also be included in the polyurethane prepolymer composition. Neutral fillers are generally preferred. Highly alkaline materials have undesirable catalytic effects, and highly acidic materials attack the urethane bonds. It is preferred to include a viscosity modifier in the prepolymer composition as described above. For descriptive convenience, plasticizers (eg terphenyl hydride) and thickeners or thixotropic agents (eg silicone-modified hydrophobic silica) can also be considered as part of the viscosity adjustment system. In addition,
These components may also have other effects on the prepolymer composition and cured product. Additionally, this viscosity adjusting system is not a main component of the polyurethane prepolymer composition and may not be included at all; however, inclusion of at least 1% by weight of a plasticizer may facilitate the introduction and dispersion of the solid curing agent. It is valid. When this one-component polyurethane composition is used as an adhesive, caulk, sealant, or anti-sag agent, it is preferred to include at least 1% by weight of a thickener or thixotropic agent. These plasticizers and thickeners are usually 25% by weight or more (solid content)
Even when these components are combined, they are not contained in an amount exceeding 25 to 35% by weight. The plasticizer is generally introduced in two portions. Small amount (e.g. 5-15% by weight (based on total solids))
is mixed with the isocyanate-capped prepolymer as a continuous phase. A further small amount (e.g., 1-5% by weight, depending on the amount of curative) is added into the premix to become a discontinuous curative-containing phase. In terms of the amount of curing agent, the amount of this second plasticizer is between 25 and 150 parts by weight per 100 parts by weight. If an organic water binder (such as an alkyl orthoformate) is used, it is generally preferred to include it in the premix. Trace amounts of alkyl orthoformates are effective in preventing undesirable side reactions with water. Therefore, the water binder may be added in an amount of 1 or 2% by weight or less based on the total composition. Certain inorganic fillers also bind moisture and prevent carbon dioxide formation and other undesirable side reactions. However, alkaline substances such as calcium oxide are generally not preferred. METHODS OF MANUFACTURE AND USE The formation of polyurethane prepolymers from polymeric polyols and isocyanate capping agents is carried out on known principles. For example, heat or a catalyst may be used to accelerate the NCO/OH reaction. When a solid curing agent is introduced into the continuous phase, this can be done through a premixing step. Mixing of the two phases can be performed using conventional mixing equipment. Similarly, organometallic catalysts, metal salt catalysts, thickeners, thixotropic agents, etc. can be introduced. The amount of volatile solvent added to the composition should be as small as possible. When this solvent is used, it is added to the continuous phase in an amount of 25% by weight or less of the total composition. However, solvents that significantly reduce the incompatibility between the continuous phase and the dispersed solid curing agent will have a significant negative impact on the stability of the one-component system of the present invention. For this reason, it is preferred not to include any solvent at all, resulting in a substantially 100% solids system. Plasticizers such as hydrogenated aromatics do not appear to have an adverse effect on the phase relationships or stability described above. Therefore, if you want to reduce the viscosity,
It is preferable to increase the amount of plasticizer rather than using a polyurethane solvent such as acetone or alcohol. Note that hydrocarbon solvents such as mineral spirits do not have the above-mentioned adverse effects. The one-component polyurethane system of the present invention can be used in the same manner as other one-component curable adhesives, coatings, sealants, caulks, patching materials, and moldable resin systems. Curing can be accomplished simply by heating the one-component system or the substrate to which it is applied. The one-component polyurethane system of the present invention uses the sheet molding compound (SMC) itself as an adhesive;
or is particularly useful for bonding it to metals such as aluminum. Also, good bonding is obtained in aluminum-to-aluminum bonding. Furthermore, it can be used to caulk a substrate as a protective or decorative layer. The resulting cured polymer or bond has good water resistance and is fully compatible with industrial standards. [Example] In this example, “NIAX polyol PCP-0310”
is a trifunctional polycaprolactane polyol with an average formula molecular weight of 900 and an apparent specific gravity (55/20℃)
1.073, average hydroxyl number 187mgKOH/g, acid value less than 0.25mgKOH/g sample, melting point 27
~32℃, moisture (at time of transportation) 0.03% by weight or less, viscosity
It is 270 centistokes (54.4℃). The maximum color tone of this polyol when melted is 100 (Pt−Co)
It is. "NIAX" is a trademark of Union Carbide Company. "HB-40" (trademark of Monsanto Company) is a high melting point hydrogenated aromatic that dissolves various polymers, rubbers, asphalts, and tars. It is a transparent, oily liquid with a maximum color shade (APHA) of 180, a maximum wetness (KF, in methanol) of 125ppm, and a refractive index of 1.560~
1.575 (25℃), specific gravity 1.001-1.007 (25℃/15.5℃),
Pour point -26℃, boiling point 180℃ (10mmHg), surface tension
40.1 dynes/cm (25℃), ignition point (COC) 345〓
(173.9℃), with a combustion point (COC) of 196℃.
This "HB-40" is chemically hydrogenated terphenyl and is insoluble in water. Its vapor pressure is 150℃
2.6mmHg at 200℃, 22mmHg at 200℃, and 95mmHg at 250℃. Viscosity is 70 centistokes at 0°C and 37.8°C.
29.0 centistokes, 3.8 centistokes at 98.9°C. This "HB-40" was used to partially replace the conventional diester type vinyl resin plasticizer. “Additive OF” (manufactured by Mobay Chemical, trade name) has a boiling point of 145°C, a specific gravity of 0.90 (20°C), and an ignition point of 36°C.
(DIN51755 sealed cup) alkyl orthoformate. It is a colorless liquid used alone or with other additives to stabilize one-component polyurethane coatings. Additionally, this additive is 2-3% for transparent coatings.
Things to add, 4 for pigmented coatings
It is recommended that ~5% be added. Also, 2
For component systems, it is said that about 1% is good. It is known that this additive can reduce the moisture sensitivity of polyurethane systems. “COCURE32” (manufactured by Cosan Chemical, USA,
New Jersey, Trademark) is a liquid organomercurial urethane catalyst containing 60% active ingredient and 20% mercury (calculated as metal). The liquid composition includes a non-reactive solvent that does not contain hydroxyl groups. COCURE32 is formulated to be compatible with polyethers, polyester polyols and polymeric isocyanates. "CAB-O-SIL TS-200" (manufactured by Cabot Corp., trademark) is a fumed silica powder that has been treated and modified with organic silicone. This treated powder is hydrophobic and has a surface area of 70±15 m ² /g.
Contains at least 99.8% silica and has a pH of about 4.7. IPDI (isophorone diisocyanate) used in the following examples was obtained from Veba-Chemie AG. This compound is a low viscosity liquid and does not crystallize at low storage temperatures.
In addition, because the molecular weight is relatively large, the vapor pressure is low.
At 20°C it is 0.0004 mbar and at 50°C it is 0.009 mbar. When the isocyanate-capped prepolymer terminal residue is encountered, its vapor pressure is further reduced along with its odor. The molecular weight of this compound is 222.3, and the NCO equivalent is 111.1. The ignition point is 155℃ (closed) and the spontaneous ignition temperature is 430℃. The minimum specified NCO content is 37.5% by weight, the minimum specified purity is 99.0% by weight, and the specified density is from 1.058 at 20℃
It is 1.064g/ml. Total chlorine is 0.05% by weight or less, and maximum hydrolyzed chlorine is 0.02% by weight or less. The melting point is -60°C and the boiling point is 158°C at 13.33 mbar. Viscosity does not exceed 150 cps at -20°C. The pentaerythritol used in this example is “PE-200” (manufactured by Hercules Incorp., trademark).
It is of commercial quality. this is
It consists of fine particles that can pass through 200 meters (US). Less than 1% of these particles
325 (US) It merely remains on the mesh. This monopentaerythritol (C
[CH ₂ OH] ₄ ) is of general industrial grade with a purity of 88±2%. The remaining 10-14% is primarily dipentaerythritol. The specified hydroxyl content is 48±1% and the ash content is less than 0.01%. Less than 0.5% of this "PE-200" is liquid by-products or impurities. The average equivalent weight is 35.4. Note that polypentaerythritol other than dipentaerythritol may also exist. Example 1 One-component Curable Polyurethane Adhesive This thixotropic adhesive was found to be suitable for bonding polyester bicycle sheet molding compound (SMC). The continuous phase of this composition is primarily IPDI-capped polycaprolactone triol mixed with a plasticizer. The discontinuous phase was introduced into a premix consisting of technical grade pentaerythritol, a plasticizer and an alkyl orthoformate. An organic mercury catalyst and hydrophobic silica were added to this composition to impart thixotropy. The components of this one-component composition, including dispersed or suspended curing agent, are listed below in order of addition. Ingredient Amount (wt%) Polyurethane prepolymer (consisting of 53.0 wt% “NIAX polyol PCP-0310” and 47.0 wt% IPDI) 73.14 “HB-40” (plasticizer) 7.31 Premix 7.8 “COCURE32” ( Catalyst) 0.25 “CAB-O-SILTS-200” (thixotropic agent)
11.5 The above premix contained "PE-200" industrial grade pentaerythritol, "HB-40" plasticizer and "Additive OF" in the ratio of 59.75:39.4:0.85 (by weight). Example 2 Spot Welding and Furnace Curing The one-component curable composition of Example 1 was used to bond acid-etched aluminum to each other and to aluminum and sheet forming compound (SMC). Rockwell for these tests.
SMC was used. The thickness of the adhesive layer was 250 to 380 μm. Spot welding was simulated using a heated pattern press. The results for SMC/SMC binding are as follows. 1 Spot welding (pattern press) Curing conditions Adhesive strength on board (temperature/time) (breakage*(psi)) 350〓/2 minutes 751 350〓/3 minutes 915 350〓/4 minutes 859 350〓/5 minutes 912 Note: *In all cases, the bond did not fail before the substrate failed. These bond strengths exceed industry standards by a factor of at least 10
It was beyond normal. 2 In-furnace curing 2 stages Adhesive strength on substrate (temperature/time) (damage** (psi)) 1st stage: 260〓/30 minutes 768 2nd stage: 330〓/30 minutes 943 (Note) **… According to industrial standards, after the first stage
100psi, 600psi after second stage or SMC failure. SMC damage was observed after both curing steps. 3 Water immersion test Water immersion test or bond strength on substrate Wet base treatment Failure (psi)) (time/temperature) 14 days immersion/75〓 675 14 days/200〓 657 14 days/100〓 688 (100% relative Humidity) We also conducted adhesion tests with various other substrates.

[Table] 〓


(SMC damage)
〓2nd stage 330〓/30
minutes

Claims (1)

[Scope of Claims] 1. An unblocked thermosetting one-component isocyanate-capped prepolymer composition that cures to a solid polymer having a molecular weight at least twice that of the prepolymer at a temperature of 60°C or higher. the prepolymer composition is (a) fluid at 60°C or higher and has a molecular weight of 250 or higher;
having a chain of repeating units selected from oxyalkylene, ester and mixtures thereof,
an unblocked aliphatic or cycloaliphatic isocyanate capped prepolymer forming a uniformly dispersed continuous phase; (b) a solid, finely divided polyol having the structural formula: (ROCH ₂ ) ₃ C− [ _{CH2OCH2C ( CH2OR} ) ₂
] _-o CH ₂ OR (wherein R is hydrogen or an aliphatic, alicyclic, or aromatic group, two or more of R is hydrogen, n is an integer from 0 to 2) Also, this polyol is at least partially incompatible with the prepolymer below 60°C, and the presence of this solid fine polyol changes the overall NCO to OH ratio of the composition from greater than 1.5:1 to 0.8: 1 to 1.5:1; and (c) an organometallic or metal salt catalyst dispersed in the continuous phase that promotes the reaction between isocyanate groups and the free hydroxyl groups of (b) above; A thermosetting one-component isocyanate-capped prepolymer composition comprising: 2 The dispersed phase is a finely divided polyol;
The thermosetting one-component isocyanate capped prepolymer composition according to claim 1, comprising active hydrogen and a plastic caustic agent inert to isocyanates mixed therein. 3. The thermosetting one-component isocyanate capped prepolymer composition according to claim 1, wherein the continuous phase is solvent-free. 4 (a) The isocyanate-capped prepolymer has an aliphatic or alicyclic diisocyanate having different reactivity -NCO groups and a polyester or polyoxyalkylene polyol at an NCO/OH ratio of 1.5:1 to 3: (b) the thermosetting polyol is an unblocked reaction product obtained by the reaction in 1, and (b) the polyol is unesterified, unreacted pentaerythritol or dipetaerythritol. Component-type isocyanate capped prepolymer composition. 5 The isocyanate capped prepolymer is
5. The thermosetting one-component isocyanate capped prepolymer composition according to claim 4, which is obtained by reacting such that the NCO/OH ratio is 2.0 or more. 6 The isocyanate-capped prepolymer of component (a) is an unblocked isophorone diisocyanate-capped trifunctional polyester polyurethane prepolymer with a molecular weight of 500 to
5,000 100% solids continuous phase; the polyol of component (b) is unreacted, unesterified pentaerythritol fine particles which are a plasticized solid phase uniformly dispersed in the continuous phase. The thermosetting one-component isocyanate capped prepolymer composition according to item 1. 7 (a) Isophorone diisocyanate capped poly(epsilon caprolactan) triol with a molecular weight of 500 to 3000, and an NCO/OH ratio of isophorone diisocyanate to the triol of 2:1 to 2:1.
3:1 reaction with a 100% solid continuous phase; (b) a plasticized solid phase comprising a moisture binder;
It consists of pentaerythritol with a purity higher than industrial grade and a plasticizer inert to OH groups and -NCO groups, and the amount of pentaerythritol increases the NCO/OH ratio of the entire composition to 1:1 to 1.5:1.
(c) an effective amount of an organometallic catalyst; and (c) an effective amount of an organometallic catalyst. 8 The isocyanate capped prepolymer of component (a) has a ratio of NCO groups to OH groups of 0.8:1 to 3.0:
1. A thermosetting one-component isocyanate capped prepolymer composition according to claim 1. 9 The above isocyanate capped prepolymer is obtained by reacting such that the NCO/OH ratio is 1.5 or more, and the amount of polyol as component (b) is
A thermosetting one-component isocyanate capped prepolymer composition according to claim 1, which reduces the NCO/OH ratio from 0.8 to 1.5. 10 The isocyanate-capped prepolymer of component (a) is an unblocked isophorone diisocyanate-capped trifunctional polyester polyurethane prepolymer with a molecular weight of 500 to
5000 100% solids continuous phase; unreacted, unesterified pentaerythritol fine particles which are plasticized solid phase in which the polyol of component (b) is uniformly dispersed in the continuous phase; NCO in doprepolymer
The ratio of groups to OH groups ranges from 0.8:1 to 3.0:1.
A thermosetting one-component isocyanate-capped prepolymer composition according to claim 1 in which the amount can be reduced to between 0.8:1 and 1.5:1. 11 (a) up to 25% by weight of a solvent; an unblocked isocyanate-capped prepolymer consisting of a polyester polyol capped with an aliphatic or cycloaliphatic polyisocyanate, which is fluid at 60°C; a continuous liquid phase having an average molecular weight of 500 or more and an isocyanate functionality of more than 1 and less than 4; (b) a plasticized solid phase dispersed in the continuous liquid phase, which Reaction monomer, dimer pentaerythritol or its ester or its 2
has at least two free hydroxyl groups, and the ratio of NCO groups to OH groups in the entire composition is 1.5:1.
(c) an organometallic or metal salt catalyst which promotes the reaction between the isocyanate groups and the free hydroxyl groups of (b) above in the continuous liquid phase; A one-component polyurethane heat-curable adhesive comprising: 12 The polyester polyol is selected from polycaptolactone glycol, triol, and tetrol, and pentaerythritol or its dimer is unesterified, and NCO/OH
12. An adhesive according to claim 11 containing an organometallic catalyst for the reaction. 13. The adhesive according to claim 12, wherein the polycaprolactane glycol, triol, and tetrol have a molecular weight of 500 to 5,000. 14 Aliphatic or alicyclic polyisocyanate is 1
Claim 1 is a diisocyanate having three aliphatic NCOs and one alicyclic NCO.
Adhesive according to item 2. 15 The polyol of component (b) is in an amount capable of reducing the ratio of NCO groups to OH groups in the entire composition from the range of 0.8:1 to 3.0:1 to the range of 0.8:1 to 1.5:1. An adhesive according to claim 11. 16 (a) Polyoxyalkylene or polyester-containing polyol with aliphatic or alicyclic polyisocyanate, NCO/OH ratio = 1.5:1 ~
capping at a ratio of 3:1 to obtain an unblocked isocyanate-capped prepolymer that is liquid at room temperature; (b) an NCO/OH ratio in the entire composition of 0.8:1 to 1.5:
uniformly dispersing in the prepolymer an amount of solid polyol fine particles sufficient to reduce
It can increase reactivity at temperatures above ℃ and below the decomposition temperature of the prepolymer, and has a structural formula of (ROCH ₂ ) ₃ C-[CH ₂ OCH ₂ C(CH ₂ OR) ₂
] - _o CH ₂ OR (wherein R is hydrogen or an aliphatic, alicyclic or aromatic acyl group, two or more of R are hydrogen, and n is an integer from 0 to 2)] A method for producing a thermosetting one-component isocyanate capped prepolymer composition. 17 The capping step uses (1) a polyester or polyoxyalkylene polyol with a functionality of 2 to 8;
(2) an aliphatic or alicyclic diisocyanate; the above polyol is non-esterified pentaerythritol; 17. The method according to claim 16, wherein the prepolymer is mixed with the aid of a prepolymer. 18 In step (a) above, the polyoxyalkylene or polyester-containing polyol is added with an aliphatic or alicyclic polyisocyanate NCO/OH ratio of 0.8:1 to
17. A process according to claim 16, which comprises capping in a ratio of 3.0:1 to obtain an isocyanate-capped prepolymer.