JP2002037828A - Method for producing polyurethane foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyurethane foam excellent in productivity whereby the temperature of a mold can rapidly be raised to a temperature capable of curing a foam material. SOLUTION: In the mechanical froth method, a gas-liquid mixed raw material containing a heat-sensitive catalyst is injected into a preheated mold at a defined temperature and the temperature is raised from a reaction starting temperature of the catalyst to the temperature over 40 deg.C within 20 minutes, especially 15 minutes by a heater equipped with the mold so that the material is cured. The heating is stopped and the mold is removed to obtain the cured foam. The heater is preferably removed before the removal of the mold. The productivity can be improved by forcibly cooling the mold through the water-cooling or the like before the removal of the mold and shortening the time to the next injection of the material into the mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heat-sensitive catalyst,
Production that can quickly raise the temperature of the mold into which the gas-liquid mixed foam material has been injected, and can shorten the time until the foam material can be injected again into the mold after curing and demolding. The present invention relates to a method for producing a polyurethane foam having excellent properties. This polyurethane foam is manufactured by a mechanical floss method, and can easily be a foam having a low density and hardness. For this reason, a toner supply roller, a transfer roller, and the like incorporated in a copying machine, a facsimile,
It can be used as various types of rollers, such as a cleaning roller, in particular, a curl removing roller that is used after being compressed and deformed, or a packing, a sealing material, or the like.

[0002]

2. Description of the Related Art In a mechanical floss method, water or a foaming agent is not added to a raw material, but an inert gas is mixed in a reaction system in advance and foaming is performed by mechanical stirring. Since the polyurethane foam obtained by this method does not contain a plasticizer, there is no risk of soiling electronic components and the like. Further, it is easy to obtain a foam having fine cells and low hardness, and is used in many applications such as various rollers of office equipment such as a copying machine, a facsimile, and a printer. Further, the polyurethane foam obtained by the mechanical floss method has no cell anisotropy unlike a flexible polyurethane foam or the like. Therefore, there is also an advantage that, when used by being brought into contact with another member such as a roller, the pressing force on the peripheral surface thereof becomes constant.

In addition, in the mechanical floss method, since a thermosetting urethane material is basically used, it is necessary to heat and cure a foam material injected into a molding die. As the heating method, there is a method of heating a mold placed on a hot plate heated by steam or the like, or a method of indirectly heating by a gas burner, air in a furnace heated by steam or the like, There is no particular limitation. However, if the mold is excessively heated at the time of injection of the foam raw material, the reaction starts immediately after the injection, and a stripe pattern or the like appears on the surface of the foam, cell roughness, pinholes, etc., and in some cases, In some cases, the foam material is not sufficiently distributed in the mold, resulting in the occurrence of underfill. Therefore, it is necessary to keep the mold at a temperature at which curing does not start at the time of injecting the raw material.After injecting the foam raw material, the molding die is heated and cured, then the mold is removed, and then the raw material is injected again Therefore, it is necessary to lower the temperature of the mold.

[0004]

However, in the case of a hot plate heated by steam or the like, after the raw material is injected into a temperature-controlled mold, the temperature is raised and cured, and the temperature is raised to a temperature at which the raw material can be injected again. It is not easy to lower the mold temperature. Furthermore,
Indirect heating by an air atmosphere in a heating furnace requires a long time to elevate the temperature of the mold to a temperature at which the curing of the foam material starts, and as a result, the foam material can be injected into the mold again. This increases the time required to complete the process and reduces productivity.

The present invention solves the above-mentioned conventional problems, uses a foam material containing a heat-sensitive catalyst and is mixed with gas and liquid, and after injecting the material, rapidly raises the temperature of the mold. An object of the present invention is to provide a method for producing a polyurethane foam excellent in productivity, which can shorten the time required for injecting the foam raw material into the molding die again by curing the polyurethane foam.

[0006]

In the mechanical froth method, first, a polyol component containing a polyol, a catalyst, a cross-linking agent, and the like and containing no foaming agent is prepared, and the polyol component, a foam stabilizer, a polyisocyanate, and the like are prepared. The resulting foam material is injected into the chamber, and at the same time, an inert gas is supplied and bubbled. Then, the foam raw material mixed in gas and liquid in the chamber is discharged into the molding die. Thereafter, the mold is heated to a required temperature to cure the foam material, thereby forming a polyurethane foam.

In this mechanical floss method, cells formed by bubbling of an inert gas tend to be broken with time. Therefore, it is preferable to raise the temperature in a short time to a temperature at which the foam material injected into the molding die can be cured, and to cure the foam material. Thus, if the process from cell formation to hardening is completed in a short time, fine and uniform cells can be formed. Further, by reducing the heating time, the time required for cooling the mold to a temperature at which the foam material can be injected again can be reduced, and the productivity can be improved. The present invention has been made based on such findings.

[0008] The method for producing a polyurethane foam according to the first invention is a method for producing a polyurethane foam by a mechanical floss method, wherein a molding die preheated to a predetermined temperature comprises:
After injecting a foam material containing a heat-sensitive catalyst and mixed in gas and liquid, the temperature of the mold is raised within 20 minutes to a temperature range exceeding the reaction start temperature of the heat-sensitive catalyst by 40 ° C. or more. It is characterized in that the raw material is cured and then released.

A method for producing a polyurethane foam according to a second aspect of the present invention is the method for producing a polyurethane foam by a mechanical floss method, wherein a foam material containing a heat-sensitive catalyst and a gas-liquid mixture is added to a mold preheated to a predetermined temperature. After the pouring, the temperature of the mold is raised by a heater arranged in the mold within 20 minutes to a temperature range exceeding the reaction start temperature of the thermosensitive catalyst by 40 ° C. or more, and the foam raw material is cooled. It is characterized in that curing is performed, heating by the heater is stopped, and then the mold is removed. In the first and second aspects of the present invention, the temperature may be lowered after the curing and before the mold is released, or may be cooled or forcedly cooled.

The temperature of the mold must be raised from a predetermined temperature to a temperature range exceeding the reaction start temperature of the thermosensitive catalyst by 40 ° C. or more within 20 minutes.
It is actually difficult to raise the temperature uniformly in less than 2 minutes. On the other hand, if it takes more than 20 minutes to raise the temperature, the cells contained in the gas-liquid mixed foam raw material start to be broken, and a sufficiently uniform foam cannot be obtained. The heating time is preferably 2 to 20 minutes, particularly preferably 5 to 15 minutes. If the heating time is within this range, a uniform foam can be obtained, and the foam material is injected again into the molding die. The time to obtain can also be shortened.

The above-mentioned "mold" may be made of any material, but a mold having good heat conductivity is preferable, and a resin mold or the like can also be used. The above-mentioned predetermined temperature and the temperature for curing in this mold are temperatures near the inner surface of the mold, and can be measured by inserting a temperature sensor into the wall of the mold.

The mold into which the foam raw material has been injected is heated to a temperature range exceeding the reaction start temperature of the heat-sensitive catalyst by 40 ° C. or more.
A temperature exceeding 0 ° C., especially 40 to 45 ° C., is sufficient, and it is not necessary to make the temperature excessively high. As the temperature after the temperature rise is closer to the temperature exceeding the reaction start temperature by 40 ° C., the time required for the temperature rise becomes shorter, and after the curing, the time required for the temperature fall becomes shorter, until the foam raw material can be injected again into the molding die. Can be shortened. Incidentally, the above-mentioned "reaction start temperature" of the heat-sensitive catalyst is such that in the heat generation curve of the foam raw material by the differential scanning calorimeter, the tangent at the inflection point on the low temperature side of the heat generation peak intersects the low temperature side base line or its extension line. This is a reading on the temperature axis corresponding to the point.

In the second invention, the type and arrangement of the “heater” are not particularly limited as long as the temperature of the mold can be raised quickly and uniformly. A planar heating element can be used as the heater. By pressing this heater against a required surface of the mold, heat is conducted through the wall of the mold and the entire mold can be easily heated. When the heating by the heater is stopped, it is only necessary to stop energizing the heater, but it is preferable to remove the heater before removing the mold as in the fourth invention. In this case, the temperature of the mold can be reduced. Further, the heater may be provided inside the wall of the mold, and the heater may be an electric heater or an oil circulation heater.

A channel for circulating a coolant such as water can be formed in the wall of the mold, and the mold can be forcibly cooled before the mold is removed as in the fifth invention. Thereby, the time until the foam material can be injected again into the mold can be greatly reduced, which is preferable. When the forced cooling is performed as described above, the cooling rate is preferably set to 30 ° C./min or less, particularly preferably 20 ° C./min or less, as in the sixth invention. When the cooling rate exceeds 30 ° C./min, the rapid cooling does not supply the total amount of heat necessary for curing the foam material injected into the molding die, resulting in a shortage, and the temperature of the molding die falls to a predetermined temperature. However, it may not be possible to remove the mold, which is not preferable.

When the polyurethane foam is produced by the method of the first to sixth inventions, after the foam raw material is injected into the mold, after curing and demolding, the temperature of the mold is lowered,
The time until the foam material can be injected again into the mold at the predetermined temperature can be set to 40 minutes or less as in the seventh invention, and the productivity can be improved. This time can be particularly set to 30 minutes or less, and if necessary, the time can be further shortened as long as the homogeneity of the foam is not impaired, and the production can be performed more efficiently.

As the above-mentioned "thermosensitive catalyst", the following various ones can be used. (1) Tertiary amine blocking salt This catalyst dissociates the blocking salt when the temperature rises,
A tertiary amine is formed and activated. As tertiary amines, triethylamine, triethylenediamine, N,
Piperazines such as N'-dimethylpiperazine and N-methyl-N'-dimethylaminoethylpiperazine;
Morpholines such as (2-dimethylaminoethyl) morpholine, imidazoles such as 1,2-dimethylimidazole, 1-methyl-1,4,5,6-tetrahydropyrimidine and 1-ethyl-1,4,5,6 Pyrimidines such as -tetrahydropyrimidine; and 1,8-diazabicyclo [5,4,0] undecene-7 (DBU). Examples of the block acid that forms a salt with these tertiary amines include phenol, octylic acid, phthalic acid, adipic acid, and sulfonic acid. As this heat-sensitive catalyst, a salt of DBU is particularly preferred.

(2) Nickel acetylacetonate This catalyst is hydrated. When the temperature rises, hydration is released and activated. (3) Iron acetylacetonate When this catalyst is heated, acetylacetone is released and activated. Iron acetylacetonate and acetylacetone are preferably used in a mass ratio of about 2: 1. As the heat-sensitive catalysts (1) to (3), only one kind may be used, or two or more kinds may be used in combination. Also,
These heat-sensitive catalysts can be used in combination with general organic catalysts and metal catalysts.

As the polyol, polyether polyol, polyester polyol, and polyether ester polyol obtained by copolymerizing polyether polyol and polyester polyol can be used.
Further, in the mechanical floss method, a polymer polyol is usually used in combination to form a foam having a sufficient tensile strength or the like. The polymer polyol is a polyol obtained by graft-polymerizing an ethylenically unsaturated compound such as acrylonitrile, styrene or methyl methacrylate with a polyether polyol at a solid content of 10 to 40% by mass, preferably 15 to 30% by mass. Say.

Examples of the polyisocyanate include tolylene diisocyanate (TDI), crude TDI, 4,4'-diphenylmethane diisocyanate (MDI), and crude MD
I, and 1,6-hexamethylene diisocyanate (H
DI), crude HDI, 1,5-naphthalene diisocyanate, paraphenylene diisocyanate, 2,2,4-
Trimethylhexamethylene diisocyanate, 2,4
4-trimethylhexamethylene diisocyanate, 4,
4'-dicyclohexylmethane diisocyanate, m-
Xylene diisocyanate, hexamethylene diisocyanate, hydrogenated MDI, isophorone diisocyanate, etc.
Various aromatic and aliphatic compounds can be used. Besides these, a prepolymer type polyisocyanate can also be used.

As the crosslinking agent, short-chain diols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, glycerin and trimethylolpropane can be used. In order to form a foam having a lower hardness, an ester oligomer chain-extended with ε-caprolactone using ethylene glycol or trimethylolpropane as an initiator, and a molecular weight of 40
It is preferable to use a crosslinking agent having a large molecular weight, such as a trifunctional polyether polyol of about 0 to 700.

As the foam stabilizer, a block copolymer of dimethylpolysiloxane and polyether can be generally used. Further, a special foam stabilizer in which an organic functional group is added to polysiloxane can be used. Thus, silicone foam stabilizers are frequently used as foam stabilizers.
In addition, raw materials generally used for urethane blending, such as an ultraviolet absorber, an antioxidant, an organic and inorganic filler, and a coloring agent, can be appropriately used as the foam raw material.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples. Example 1 Polymer polyol (trade name “P” manufactured by Mitsui Chemicals, Inc.)
OP2430 ") 90 parts by mass (hereinafter abbreviated as" part "), 8 parts of polyester polyol (trade name" PCL305 ", manufactured by Daicel Chemical Industries, Ltd.), heat-sensitive catalyst (nickel acetylacetonate, reaction start temperature; 65)
° C, manufactured by OSi Specialties Inc., trade name “LC-5”
615 ") and 2 parts of an amine-based catalyst (trade name" DABCO-33LV "manufactured by Sankyo Air Products Co., Ltd.).
One part was mixed and stirred to prepare a polyol component.

Thereafter, the polyol component, 8 parts of a silicone-based foam stabilizer (trade name "L-5614", manufactured by OSi Specialties, Inc.) and 14 parts of polyisocyanate (trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) "MT
L ") into the chamber and add 0
At 1 ° C. and 1 atm, nitrogen gas was supplied at a flow rate corresponding to 200 cm ³ / min. Then, the foam was mixed and stirred in a chamber, and the prepared foam was poured into a mold having a surface heating element attached to the surface and adjusted to 90 ° C., and then heated to 120 ° C. in 5 minutes. Raise the temperature to 5
The foam was allowed to cure for a minute. Next, the sheet heating element was removed from the surface of the mold, allowed to cool, and then removed after 10 minutes. Thereafter, when the mold was left to cool for 5 minutes, the temperature of the mold dropped to 90 ° C. at which the foam material could be injected. The Asker C hardness of the obtained cylindrical polyurethane foam was 20 °.

Comparative Example 1 A foam material having the same composition as in Example 1 was mixed and stirred in the same manner as in Example 1, and the foam was prepared and heated to 90 ° C. in a heating furnace controlled by a gas burner. The mold was poured into a heated mold, and the mold was placed again in a heating furnace, and the furnace temperature was adjusted to 160 ° C. However, it took a long time of 20 minutes to raise the temperature to 120 ° C. Also,
Since the set temperature of the furnace was 160 ° C., the temperature in the heating furnace after curing for 5 minutes was increased to 130 ° C. Here, the mold was taken out of the furnace, left to cool as it was, and after the mold was released, further cooling was continued. However, it took 25 minutes to lower the temperature of the mold to 90 ° C. at which the foam material could be injected. Needed. The Asker C hardness of the obtained polyurethane foam was 20 °, and the foam was low in hardness as in Example 1. However, since a long time had passed until the foam hardened, the foam formed was partially broken, and the foam was not as homogeneous as in Example 1.

FIG. 1 shows injection of a foam material into a molding die,
4 is a graph schematically showing a change over time of the temperature of a mold during the process of raising, hardening, and lowering the temperature in Example 1 and Comparative Example 1. As can be seen from this graph, in Comparative Example 1, the time required to cool the foam material from the injection of the foam material to the molding die to the temperature at which the foam material can be injected again after curing and demolding is 50 minutes. On the other hand, in the first embodiment, the time is reduced to half, that is, 25 minutes.

It should be noted that the present invention is not limited to the above specific embodiments, but can be variously modified within the scope of the present invention depending on the purpose and application. For example, the foam may have various shapes such as a columnar shape, a rectangular parallelepiped shape, etc. as well as a cylindrical shape.

[0027]

According to the first and second aspects of the present invention, the time required to raise the temperature of the mold to a temperature at which the foam material can be cured can be considerably shortened. As a result, after demolding, the time required to lower the temperature to a temperature at which the foam material can be injected again into the molding die can be shortened, and this time can be reduced to 40 minutes or less as in the seventh invention. it can.

[Brief description of the drawings]

FIG. 1 shows the change over time of the temperature of a molding die during foam production.
4 is a graph schematically showing a comparison between Example 1 and Comparative Example 1.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) B29K 75:00 B29K 75:00 105: 04 105: 04 F term (Reference) 4F204 AA31 AA42 AB02 AG08 AG20 AK01 AR06 EA01 EB01 EE06 EE21 EF01 EF27 EK13 EK15 EL04 EL15 4J034 BA03 CA04 CA05 CB03 CB07 CC03 CC08 DA01 DB03 DF01 DF12 DG00 DH00 DQ05 DQ15 DQ16 DQ18 DQ28 HA07 HC03 HC12 HC13 HC22 HC46 HC52 HC61 KB64 HC04 HC04 PA02 PA03 PA05 QA05 QC01 RA08 RA16

Claims (7)

[Claims] In a method for producing a polyurethane foam by a mechanical floss method, a foam material containing a heat-sensitive catalyst and containing a gas-liquid mixture is injected into a mold preheated to a predetermined temperature. A method for producing a polyurethane foam, comprising raising the temperature within 20 minutes to a temperature range exceeding the reaction start temperature of the heat-sensitive catalyst by 40 ° C. or more, curing the foam raw material, and then demolding the polyurethane foam. 2. A method for producing a polyurethane foam by a mechanical froth method, comprising: injecting a foam material containing a heat-sensitive catalyst and mixed in a gas-liquid state into a mold preheated to a predetermined temperature, and then disposing the foam material in the mold. The temperature of the mold was raised to 40 ° C. by the heater.
A method for producing a polyurethane foam, comprising raising the temperature within 20 minutes to a temperature range exceeding the above, curing the foam raw material, stopping the heating by the heater, and then removing the mold. 3. When the reaction initiation temperature is t (° C.)
The predetermined temperature t ₀(° C.), t ≦ t₀≤ (t + 40)
The polyurethane foam according to claim 1 or 2,
Production method. 4. The method for producing a polyurethane foam according to claim 2, wherein the heater is removed before the demolding. 5. The method for producing a polyurethane foam according to claim 1, wherein the mold is forcibly cooled before the mold is released. 6. The method for producing a polyurethane foam according to claim 5, wherein the forced cooling rate is 30 ° C./min or less. 7. The method for producing a polyurethane foam according to claim 1, wherein the time from the time of the injection until the foam material can be injected again into the molding die is 40 minutes or less. .