JPH0528263B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to polyethylene compositions. Conventional technology In the past, polyethylene was coated on the inner and outer surfaces of metal pipes, metal plates, electric cables, steel wires, etc. to improve the corrosion resistance, appearance, and food hygiene of metals, or to overcome the drawbacks of various synthetic resins. In order to improve this, composites made by laminating polyethylene are known. In this case, the polyethylene is a composition of modified polyethylene, which is obtained by modifying polyethylene with an unsaturated carboxylic acid or a derivative thereof to give adhesive properties, and synthetic rubber in order to improve its adhesion to metals and various synthetic resins. Are known. For example, a composition consisting of a hydrocarbon synthetic rubber and a modified ethylene polymer that is substantially a medium-low pressure ethylene polymer having a specific melt index ratio grafted with an unsaturated carboxylic acid or a derivative thereof No. 120750), polyethylene modified with an unsaturated carboxylic acid or its anhydride added with a specific ethylene/α-olefin random copolymer is heat-bonded to a metal body coated with an epoxy resin adhesive and heat-treated. How to
168628), a laminate in which metal foil is laminated with sheets of modified polyethylene and polyisobutylene interposed therebetween (Japanese Unexamined Patent Publication No. 56-93541), and the like have been proposed. On the other hand, in order to improve the adhesion between metals and thermoplastic resins and polyethylene and their durability, compositions of polyethylene and synthetic rubber obtained by modifying specific selected low-density polyethylene with unsaturated carboxylic acids or derivatives thereof ( Unexamined Japanese Patent Publication 1987-
165413) and a composition in which a mixture of specific linear low-density polyethylene and synthetic rubber is modified by reacting an unsaturated carboxylic acid or a derivative thereof (Japanese Patent Application Laid-open No. 165469/1982) has also been proposed. Problems to be Solved by the Invention Although the composition and method proposed above improve the adhesive strength between polyethylene and adherends such as metals and thermoplastic resins, the adhesive strength at low preheating temperatures of the adherend is There wasn't enough about that. That is, the modified polyethylene or its composition will not exhibit sufficient adhesion unless it wets the adherend at a temperature higher than the melting point of the resin. Therefore, the adherend is usually preheated to a temperature close to the melting temperature of the resin, and its surface is coated with the molten resin. However, when coating a metal object multiple times, for example when coating the inner and outer surfaces of a steel pipe, preheating the steel pipe whose inner surface has been coated first to near the melting point of the resin will soften the already coated surface. Because of the risk of damage and peeling, a resin was needed that could be bonded even if the preheating temperature of the steel pipe was lowered. Further, if the preheating temperature of the adherend cannot be lowered, the cooling temperature after coating is lowered to coat the adherend, resulting in a problem that the line speed (production speed) decreases. As having sufficient adhesion even when the preheating temperature of the adherend is lower than before,
The present inventors previously proposed a modified polyethylene composition (Japanese Patent Application No. 1982-99621) consisting of a modified linear low density polyethylene having a specific melt index and polyisobutylene. However, although this composition has sufficient contactability even when the preheating temperature is lowered, it has poor mechanical strength after cooling, such as threading of pipe ends or There remained room for improvement in the practical strength against the torque applied by tightening with a pipe wrench during piping. The present invention solves the above-mentioned problems, has excellent adhesion even when the preheating temperature of the adherend is lowered compared to conventional products, and has high practical mechanical strength. The object of the present invention is to provide a polyethylene composition having the following properties. Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors found that a modified linear low-density polyethylene with a specific range of melt index (hereinafter referred to as MI), The present invention was completed based on the discovery that a composition consisting of two types of linear low-density polyethylene, one with low MI and one with high MI, and polyisoptylene and/or a modified product thereof can achieve the object of the present invention. That is, the present invention provides (A) 10-85% by weight of modified polyethylene obtained by reacting linear low-density polyethylene with an MI of 7-50 g/10 min with an unsaturated carboxylic acid or a derivative thereof, (B) an MI of 0.1-85% by weight. 5g/10min linear low density polyethylene 5-80% by weight, (C) MI12-50
g/10 min linear low density polyethylene 5-80% by weight
and (D) a polyethylene composition comprising 5 to 50% by weight of polyisobutylene and/or a modified polyisobutylene obtained by reacting the polyisobutylene with an unsaturated carboxylic acid or a derivative thereof. Linear low-density polyethylene (hereinafter referred to as (A) LLDPE) used in the present invention (A) MI7 to 50 g/10 minutes
is a method of converting ethylene and α-olefins, such as butene-1, pentene-1, hexene-1, and 4-methylpentene, in the presence of a chromium-based or Ziegler-based catalyst by a low-pressure gas-phase, solution or liquid-phase method. −
1, manufactured by copolymerizing with heptene-1, octene-1, etc., and has an MI of 7.
-50 g/10 minutes, preferably 8-20 g/10 minutes. Here, α-olefin is generally 3 to 20
Contained in % by weight. Among these (A) LLDPEs, the density of polymerized by low pressure gas phase method is 0.905~
It is desirable that the weight average molecular weight w/number average molecular weight n be 0.950 g/cm ³ and 3 to 12. Above (A)
When the MI of LLDPE is less than 7 g/10 min, adhesion is insufficient at low preheating temperature of the adherend;
If it exceeds g/10 minutes, the strength of the resin will be insufficient. Furthermore, polyethylenes other than linear low-density polyethylene do not have sufficient adhesion to the adherend and their durability. Linear low-density polyethylene (hereinafter referred to as (B) LLDPE) used in the present invention (B)MI0.1-5g/10min
is manufactured in the same way as (A)LLDPE above,
In particular, the MI is 0.1 to 5 g/10 minutes. low
(B)LLDPE formulation of MI can improve mechanical strength without compromising adhesion and its durability. Linear low-density polyethylene (hereinafter referred to as (C)LLDPE) used in the present invention (C)MI12-50g/10min
is manufactured in the same way as (A) LLDPE above,
Especially those with MI of 12 to 50 g/10 min. High MI
(C) The blending of LLDPE can improve the adhesion at low preheating temperatures of the adherend. Commercially available polyisobutylene can be used as the polyisobutylene used in the present invention, but Mooney viscosity (ML ₁₊₄ , 100
℃, JIS K-6300) is 10 to 150, and crystallinity (X-ray diffraction method) is preferably 30% or less. Furthermore, synthetic rubbers other than polyisobutylene do not have sufficient adhesion to adherends. Examples of unsaturated carboxylic acids used in the present invention include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, endobicyclo[2,2,1]-1,4,5,6,
7,7-hexachloro-5-heptene-2,3-
dicarboxylic acid, endobicyclo-[2,2,
1]-5-heptene-2,3-dicarboxylic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, and the like. Further, examples of derivatives of unsaturated carboxylic acids include acid anhydrides and esters, such as maleic anhydride, citraconic anhydride, endobicyclo-[2,2,1]-1,4,5,6,
7,7-hexachloro-5-heptene-2,3-
dicarboxylic anhydride, endobicyclo-[2,
2,1]-5-heptene-2,3-dicarboxylic anhydride, cis-4-cyclohexene-1,2-dicarboxylic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate , butyl methacrylate, maleate ester (monoester, diester)
etc. can be mentioned. (A) Various known methods can be used to react LLDPE or polyisobutylene with an unsaturated carboxylic acid or a derivative thereof. For example, (A) LLDPE or polyisobutylene and an unsaturated carboxylic acid or its derivative in the presence or absence of a solvent and an organic peroxide reaction initiator, such as ditertiary butyl peroxide, dicumyl peroxide, Benzoyl peroxide, 2,5-dimethyl-
2,5-di-(tert-butylperoxy)-
hexyne-3,2,5-dimethyl-2,5-di-
(tert-butylperoxy)-hexane, etc. is added and mixed in advance with a mixer such as a Henschel mixer or a ribbon blender, and the mixture is passed through a Banbury mixer, single-screw or multi-screw extruder to a temperature higher than the melting point of polyethylene or polyisobutylene. Melt and knead at a temperature below 280℃. Alternatively, (A) LLDPE or polyisobutylene may be dissolved in a solvent, and an unsaturated carboxylic acid or its derivative and a reaction initiator may be added to the solution to cause the reaction. (A) The amount of unsaturated carboxylic acid or its derivative added to LLDPE or polyisobutylene is 0.01
~3% by weight is preferred. Therefore, the amount of the unsaturated carboxylic acid or its derivative and the organic peroxide reaction initiator added is 0.05 to 5 parts by weight of the unsaturated carboxylic acid or its derivative per 100 parts by weight of unmodified LLDPE or polyisobutylene. Reaction initiator 0.001~0.5
Parts by weight are preferred. Note that if the content of unsaturated carboxylic acid or its derivative in the modified polyethylene or modified polyisobutylene obtained is less than 0.01% by weight, the strong adhesive strength of the present invention cannot be obtained;
No increase in adhesion was observed when the amount exceeded % by weight;
This increases the occurrence of gel-like substances and discoloration, which is economically disadvantageous. Next, the polyethylene composition of the present invention has (A)
Modified polyethylene of LLDPE 10 to 85% by weight, preferably 20 to 50% by weight, (B) LLDPE 5 to 80% by weight, preferably 5 to 30% by weight, (C) LLDPE 5 to 80% by weight,
Desirably 10 to 50% by weight, and 5 to 50% by weight of polyisobutylene and/or modified polyisobutylene,
It desirably consists of 15 to 40% by weight. If the content of modified polyethylene, (C) LLDPE, modified polyisobutylene and/or modified polyisobutylene is outside the above range, adhesion to adherends with low preheating temperatures will be insufficient. Furthermore, if the content of (B) LLDPE is less than 5% by weight, the mechanical strength will be insufficient, while if it exceeds 50% by weight, the adhesiveness will be insufficient, which is not preferable. The production of the composition of the present invention consists of modified LLDPE(B)
It is obtained by mixing LLDPE, (C)LLDPE, and polyisobutylene and/or modified polyisobutylene at the above-mentioned mixing ratio. In order to uniformly disperse each of the above components and make a composition with phytophilic properties, for example, pre-mix using a Henschel mixer, ribbon blender, etc., and then mix this mixture using a Banbury mixer, roll, extruder, etc. A method of melt-kneading at a temperature above the melting point of the composition and below 280°C is desirable. In addition, when polyisobutylene is in the form of a veil, it is desirable to heat and melt-knead it using a Banbury mixer, rolls, or the like. Further, the composition of the present invention is a mixture of (A) LLPDE and polyisobutylene in the above-mentioned mixing ratio, which is reacted with an unsaturated carboxylic acid or a derivative thereof, and (B) LLDPE and (C) LLDPE. It may be something. Furthermore, unmodified polyisobutylene may be mixed into this modified mixture at the above-mentioned mixing ratio. The composition of the present invention may contain various additives, such as heat stabilizers, ultraviolet absorbers, nucleating agents, antistatic agents, colorants, etc., and various fillers, such as inorganic fillers, plasticizers, etc. I can do it. These additives, etc.
They may be mixed during or after preparation of the composition. The polyethylene compositions of the present invention can then form suitable laminates with metals or thermoplastics. Metals in the laminate using the modified polyethylene composition of the present invention include iron, aluminum,
Copper, zinc, nickel, tin, stainless steel, brass, tin, galvanized iron, etc. in plate, foil, cylindrical, tubular,
Examples include lines or other shapes. In addition, as thermoplastic resins, nylon 6, nylon 66, nylon 11, nylon 12, nylon 6
Polyamides such as -10, polyolefins such as homopolymers of olefins such as polyethylene, polypropylene, and polybutene or copolymers thereof, resins that are partially acetalized polyvinyl alcohol (vinylon), and ethylene-vinyl acetate copolymers. Examples include partially hydrolyzed resin (EVAL), polyesters such as polyethylene terephthalate and polybutylene terephthalate, and polyvinyl chloride, with nylon and vinylon being particularly preferred. A laminate using the polyethylene composition of the present invention can be obtained by laminating the modified polyethylene composition of the present invention and one selected from the aforementioned metals or thermoplastic resins. The method of obtaining the laminate is not particularly limited, and examples include a method of forming each into a film or sheet and then thermocompression bonding, a method of laminating outside the die, a method of laminating (coextrusion) inside the die, a tube shape or a sheet. Known methods such as extrusion coating or powder coating can be used. In addition, when laminating with metal, pretreatments such as solvent degreasing, pickling, shot blasting, zinc phosphate treatment, calcium phosphate, etc. are usually performed, and an epoxy resin primer is used as a primer treatment to make the material stronger. A laminate with excellent adhesive strength can be obtained. As the epoxy resin primer, a one-component or two-component modified epoxy resin primer is preferred from the viewpoint of heat resistance or stability. The structure of the laminate using the polyethylene composition of the present invention is basically a two-layer structure in which the modified polyethylene composition of the present invention is laminated with one selected from the above-mentioned metals or thermoplastic resins. Various combinations can be made. For example, modified polyethylene composition (hereinafter referred to as the composition)/metal, the composition/thermoplastic resin, the composition/metal/
A combination of the composition, metal/composition/metal, metal/composition/thermoplastic resin, thermoplastic resin/composition/thermoplastic resin, etc., further combining these or other substances, For example, fibers, paper, wood boards, etc. can be combined. The composition of the present invention forms a suitable composite (coating, lamination, etc.) with metal or thermoplastic resin as described above, and is particularly useful for coating metal pipes.
An example of manufacturing a resin-coated metal tube will be described below. The base metal tube is cleaned by surface treatment such as shot blasting, grid blasting, or pickling. Furthermore, it is desirable to apply an epoxy adhesive or the like on this as a primer treatment in order to obtain a resin layer with stronger adhesive strength. The pretreated metal tube is heated to a desired temperature, such as 100°C or higher, preferably 110 to 150°C, by high-frequency induction heating or the like.
The outer surface of the metal tube is coated with the composition by extruding it into a tube shape or wrapping it into a sheet shape at a temperature above the melting point, preferably from 200 to 230°C. The thickness of the coating varies depending on the purpose, but is usually around 0.3 mm. Further, an exterior material such as polyolefin, preferably high-density polyethylene, is extruded onto the tube at a temperature above the melting point, preferably from 200 to 230 DEG C., or wrapped in a sheet, and immediately cooled with water. The thickness of the exterior material is usually about 2 mm. Note that the covering of the exterior material may be omitted as appropriate depending on the application. In addition, when applying the above-mentioned metal pipe coating to both the inside and outside of the metal pipe, the pretreated metal pipe should be coated with 100%
It is heated to ~150°C, and the inner surface is powder coated with the composition and polyolefin, preferably polyethylene, in this order to form a resin layer. Next, this inner-coated metal tube is heated to a temperature of 100° C. to less than the melting point of the inner-coated resin, and the outer surface of this metal tube is coated with the composition and polyolefin in the same manner as described above. Effects of the Invention The composition of the present invention is superior to modified polyethylene compositions that have already been proposed, from lower preheating temperatures to higher temperatures for adherends such as metals and thermoplastic resins. It shows the adhesion strength. Therefore, in multilayer resin coating, there is no inconvenience caused by softening or melting of the already coated layer, and there is no need to slow down the cooling rate after coating, so there is no reduction in production rate. In addition, the composition of the present invention has improved mechanical strength after adhesion compared to conventional compositions, so it can provide sufficient strength for practical use, such as thread cutting resistance and pipe wrench torque resistance, in resin-coated steel pipes, for example. have Due to the excellent properties described above, the composition of the present invention is suitable for composites with metals and thermoplastic resins, particularly for multilayer composites. As an example of compounding,
Inner and outer surfaces of steel pipes and cast iron pipes, coatings of steel plates, metal foils, electric cables, steel wires, etc., tank linings, multilayer films with various thermoplastic resins,
Examples include laminates such as sheets, bottles, containers, etc. Examples Next, the present invention will be explained in detail by giving examples. In addition, all parts and percentages in the examples are based on weight, and the test method is as follows. (1) MI ASTM D-1238 E (190℃, 2160g) (2) Peel strength After electrolytically degreasing a pickled steel plate (SS-41) 100 x 100 x 0.3 mm, preheat it to the specified temperature on a heating plate. , on which a sheet of the composition of the present invention (thickness 1
A test piece was prepared by heating a sheet of high-density polyethylene (3 mm thick) to 220°C, melting it, and bonding it, leaving it for 10 seconds, and cooling it by immersing it in running water. The resin layer of the test piece was cut to a width of 10 mm, a portion was peeled off as a gripping margin, and the 90° peel strength was measured at 23 mm at a peel rate of 50 mm/min using an Instron tensile tester.
℃ and 50℃. (3) Tensile modulus JIS K 7113 (Crosshead speed 0.5cm/
(4) Shear adhesive strength JIS K 6850 (5) Thread cutting test Test using SGP-PC pipe machine specified in Japan Water Works Association standard JWW AK 132-1982 (polyethylene powder-lined steel pipes for water supply) The maximum temperature at which thread cutting was possible was measured by varying the ambient temperature depending on the thread cutting method. (6) Pipe wrench tightening torque test Using a vise and a pipe wrench as described in the Japan Water Works Steel Pipe Association standard WS-033-84 (polyethylene powder-lined steel pipes for water supply, single-layer polyethylene coating on the outside), the coating was fixed in a vise. The steel pipe was tightened with a pipe wrench, torque was applied, and the torque at which the resin layer deformed was measured. The ambient temperature was 50°C. Examples 1 to 9, Comparative Examples 1 to 4 Each LLDPE with different MI (comonomer: butene-
1) Add 0.6 parts of maleic anhydride and 0.025 parts of 2,5-dimethyl-2,5-di-(tert-butylperoxy)-hexyne-3 to 100 parts, mix with a Henschel mixer, and mix this mixture into a 65 mmφ −
It is fed to a screw extruder and melt-kneaded at a set temperature of 230℃ and a screw rotation speed of 60rpm to modify it with maleic anhydride.
Got LLDPE. This modified LLDPE and polyisobutylene [manufactured by Etsuo Chemical Co., Ltd., Vistanex MML-
80 (product name)], MI0.1-5g/10 minutes undenatured LLDPE
(B) and unmodified LLDPE (C) with MI 12-50 g/10 min.
were blended in the proportions shown in Table 1, and heated and melted and kneaded at 230°C to obtain a composition. The physical properties of each composition obtained, and the peel strength and shear adhesive strength of laminates made with each composition with steel plates at each preheating temperature were measured, and the results are shown in the table below.
Shown in 1. For comparison, LLDPE with MI 5g/10min or less
When a modified product is used, ethylene butene rubber [manufactured by Mitsui Petrochemical Co., Ltd., A-4085] is used instead of polyisobutylene.
(Product name), EBR] and undenatured
In the case where LLDPE (B) was not added, a composition was prepared and a laminate was prepared in the same manner as in the example, and each physical property was measured, and the results are also listed in Table 1.

【table】

[Table] Example 10, Comparative Example 5 A 50 mmφ SGP black tube was descaled by pickling treatment as a test metal tube, and then heated to each temperature shown in Table 2 by high frequency induction heating, and the steel tube was heated to the temperature shown in Table 2.
The polyethylene composition used for
The resin-coated steel pipe was extruded and coated into a tube at a speed of m/min, and cooled in a water tank with a distance of 3 cm from the die to obtain a resin-coated steel pipe. The peel strength and physical properties of the obtained coated steel pipe were measured and the results are shown in Table 2. For comparison, a resin-coated steel pipe was obtained in the same manner as in Example 10, except that the composition of Comparative Example 4 was used. The peel strength and physical properties of the obtained coated steel pipe are also listed in Table 2.

[Table] Examples 11 and 12 After mixing (A) LLDPE and polyisobutylene used in Example 3 in the proportions shown in Table 3, this mixture was reacted with maleic anhydride in the same manner as in Example 1. A denatured mixture was obtained. LLDPE (B) and LLDPE (C) were mixed into the obtained modified mixture in the proportions shown in Table 3 to obtain a composition. A laminate with a steel plate was prepared using the obtained composition, and each physical property was measured, and the results are shown in Table 3.

【table】

【table】

Claims (1)

[Claims] 1 (A) Modified polyethylene obtained by reacting linear low-density polyethylene with a melt index of 7 to 50 g/10 min with an unsaturated carboxylic acid or a derivative thereof.
10-85% by weight, (B) Melt index 0.1-5
(C) 5-80% by weight of linear low-density polyethylene with a melt index of 12-50 g/10 min, and (D) polyisobutylene and/or the polyethylene. A polyethylene composition comprising 5 to 50% by weight of a modified polyisobutylene obtained by reacting isobutylene with an unsaturated carboxylic acid or a derivative thereof.