JPH0528265B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to modified polyethylene compositions. Conventional technology In the past, polyethylene was coated on the inner and outer surfaces of metal pipes, metal plates, electric wire 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 laminated with metal foil through a sheet made of modified polyethylene and polyisobutylene (Japanese Unexamined Patent Publication No. 1983-93541), modified high-density polyethylene, copolymer of ethylene and α-olefin A multilayer laminate structure of a polyamide and a polyethylene composition combined with a rubber-like polymer as required (Japanese Patent Application Laid-open No. 121058/1983) has 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, in which specific linear low-density polyethylene is modified with unsaturated carboxylic acids or derivatives thereof ( Japanese Patent Publication No. 57-165413
(Japanese Patent Application Laid-Open No. 2003-120012) and a composition obtained by reacting a mixture of a specific linear low-density polyethylene and synthetic rubber with an unsaturated carboxylic acid or a derivative thereof (Japanese Patent Application Laid-open No.
57-165469) has also been proposed. Problems to be Solved by the Invention Although the adhesive strength between polyethylene and adherends such as metals and thermoplastic resins has been improved in the composition and method proposed above, the adhesion at low preheating temperatures of the adherends has been improved. There wasn't enough about sex. That is, the modified polyethylene or its composition will not exhibit sufficient adhesion unless it is applied to an adherend at a temperature equal to or 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. Furthermore, if the preheating temperature of the adherend cannot be lowered, the cooling rate after coating is slowed down to coat the adherend, resulting in a problem of reduced line speed (production speed). 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. 60-99621) consisting of linear low-density polyethylene having a specific melt index, a modified product, and polyisobutylene. However, although this composition has sufficient adhesion even when the preheating temperature is lowered, the 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. An object of the present invention is to provide an adhesive 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 linear low density polyethylene modified product with a melt index (hereinafter referred to as MI) in a specific range, The present invention was completed by discovering that a composition comprising polyisobutylene and/or a modified product thereof and high-density polyethylene achieves the object of the present invention. That is, the present invention is a modified polyethylene obtained by reacting (A) linear low-density polyethylene with an MI of 7 to 50 g/10 min with an unsaturated carboxylic acid or a derivative thereof.
10-90% by weight, (B) unmodified polyethylene (excluding high-density polyethylene) 0-85% by weight,
(C) 5 to 50% by weight of high-density polyethylene and/or modified high-density polyethylene obtained by reacting the high-density polyethylene with an unsaturated carboxylic acid or its derivative; and (D) polyisobutylene and/or the polyisobutylene is unsaturated. Modified polyisobutylene 5 to 50 obtained by reacting carboxylic acid or its derivative
The gist is an adhesive polyethylene composition consisting of % by weight. The linear low density polyethylene (hereinafter referred to as LLDPE) used in the present invention has an MI of 7 to 50 g/10 min.
In the presence of a chromium-based or Ziegler-based catalyst,
Ethylene and α-olefins, such as butene-1, pentene-
1, hexane-1, 4-methylpentene-1, heptene-1, octene-1, etc., and is produced by copolymerization with MI of 7 to 50.
g/10 minutes, preferably 8 to 20 g/10 minutes. The α-olefin is generally contained in an amount of 3 to 20% by weight. Among these LLDPEs,
Density polymerized by low pressure gas phase method is 0.905 to 0.950g/
cm ³ , weight average molecular weight w/number average molecular weight n is 3
~12 is preferred. MI of above LLDPE is 7
If it is less than 50 g/10 minutes, the adhesion at a low preheating temperature of the adherend will be insufficient, while if it exceeds 50 g/10 minutes, the strength of the resin will be insufficient. Also, MI7~
For polyethylene other than 50g/10min LLDPE,
Adhesion to the adherend and its durability are insufficient. The unmodified polyethylene (excluding high-density polyethylene) used in the present invention is an ethylene homopolymer or copolymer, preferably with a density of 0.910 to
Examples include those with an MI of 0.940 g/cm ³ and an MI of 0.1 to 50 g/10 min. For example, linear low-density polyethylene (hereinafter referred to as
LLDPE), low density polyethylene (hereinafter referred to as
LDPE), medium density polyethylene (hereinafter referred to as
MDPE) or with an ethylene content of 50% by weight
The above examples include copolymers of ethylene and α-olefin or vinyl monomers. High-density polyethylene used in the present invention (hereinafter referred to as
As is well known, HDPE is a polyethylene with a density of 0.941 to 0.970 g/cm ³ obtained by polymerization using a medium-low pressure method, and an MI of 0.1 to 50 g/10 minutes, preferably 1 to 20
g/10 minutes. By blending a specific amount of HDPE, mechanical strength can be improved without reducing adhesiveness. Commercially available polyisobutylene can be used as the polyisobutylene used in the present invention, but Mooney viscosity (Ml ₁₊₄ , 100
℃, JIS K-6300 and below) 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, endo-bicyclo[2,2,1]-1,4,5, 6,
7,7-hexacyclo-5-heptene-2,3
-dicarboxylic acid, endo-bi-cyclo-[2,2,
1]-5-heptene-2,3-dicarboxylic acid, cis-4-cyclohexane-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, endo-bi-cyclo-[2,2,1]-1,4,5,6 ,7,
7-hexachloro-5-heptene-2,3 dicarboxylic anhydride, endo-bicyclo-[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 , maleic acid esters (monoesters, diesters), and the like. Various known methods can be used to react LLDPE, HDPE, or polyisobutylene with an unsaturated carboxylic acid or a derivative thereof. for example,
LLDPE, HDPE, or polyisobutylene and an unsaturated carboxylic acid or its derivative are combined with an organic peroxide initiator, such as di-tertiary-butyl peroxide, dicumyl peroxide, benzoyl, in the presence or absence of a solvent. - oxide,
2,5-dimethyl-2,5-di-(tertiary)
butylperoxy)-hexane-3,2,5-dimethyl-2,5-di-(tertiary-butylperoxy)-hexane, etc. are added, and the mixture is mixed in advance with a mixer such as a Henschel mixer or a ribbon blender. are melt-kneaded using a Banbury mixer, single-screw or multi-screw extruder at a temperature above the melting point of polyethylene or polyisobutylene and below 280°C.
Alternatively, LLDPE, HDPE, or polyisobutylene may be dissolved in a solvent, and an unsaturated carboxylic acid or a derivative thereof and a reaction initiator may be added to the solution to cause the reaction. Here, the amount of unsaturated carboxylic acid or its derivative added to LLDPE, HDPE or polyisobutylene is preferably 0.01 to 3% by weight. 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, HDPE or polyisobutylene. part, reaction initiator 0.001 to 0.5 weight is preferred. In addition, the content of unsaturated carboxylic acid or its derivative in the modified polyethylene or modified polyisobutylene obtained is 0.01
If it is less than 3% by weight, the strong adhesive strength of the present invention cannot be obtained, while if it exceeds 3% by weight, no increase in adhesive strength is observed, and the generation of gel-like substances and discoloration increase, which is also economically disadvantageous. It is. Next, the adhesive polyethylene composition of the present invention is
Modified polyethylene 10~90% by weight, preferably 20~
50% by weight, unmodified polyethylene (excluding HDPE) 0-85% by weight, preferably 0-70% by weight,
It consists of 5-50% by weight, preferably 5-40% by weight of HDPE and/or modified HDPE, and 5-50% by weight, preferably 5-40% by weight of polyisobutylene and/or modified polyisobutylene. If the content of modified polyethylene, unmodified polyethylene, polyisobutylene and/or modified polyisobutylene is outside the above range, adhesion to adherends with low preheating temperatures will be insufficient. Furthermore, if the HDPE content is less than 5% by weight, the mechanical strength is insufficient.
On the other hand, if it exceeds 50% by weight, the adhesion to adherends with low preheating temperatures will be insufficient and the object of the present invention cannot be achieved. The composition of the present invention is prepared by combining modified LLDPE and polyisobutylene and/or modified polyisobutylene.
Furthermore, it can be obtained by mixing these and unmodified polyethylene at the above-mentioned mixing ratio. In order to uniformly disperse each of the above ingredients to create a composition with palatable properties, for example, use a Henschel mixer in advance,
A preferred method is to perform preliminary mixing using a rib blender, etc., and then melt-knead this mixture using a Banbury mixer, roll, extruder, etc. at a temperature from above the melting point of the composition to 280° C. or below. 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 may be one in which an unsaturated carboxylic acid or a derivative thereof is reacted with a mixture of LLDPE, HDPE, and polyisobutylene in the above-mentioned mixing ratio. Furthermore, unmodified polyethylene, HDPE and/or
Alternatively, unmodified polyisobutylene may be mixed in the above blending 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 modified 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 olefin homopolymers such as polyethylene, polypropylene, and polybutene or their copolymers, 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 modified polyethylene composition of the present invention can be obtained by laminating the modified polyethylene composition of the present invention, the above material, and a material selected from 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 further, by using an epoxy resin primer as a primer treatment,
A laminate with stronger 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 modified 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 a material selected from the above metals or thermoplastic resins, but as necessary. Various combinations can be made. For example, a modified polyethylene composition (hereinafter referred to as the composition)/
Metal, the composition/thermoplastic resin, the composition/metal/the composition, metal/the composition/metal, metal/the composition/thermoplastic resin, thermoplastic resin/the composition/thermoplastic resin, etc. It is also possible to combine these and other materials such as fibers, paper, wood boards, etc. 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 shotplast, gridplast, 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, if the above metal pipe coating is applied 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 has sufficient strength for practical use, such as thread cutting resistance and pipe wrench torque resistance in coated steel pipes, for example. . 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,
The inner and outer surfaces of steel pipes and cast iron pipes, coatings of steel plates, metal foils, electric wire cables, steel wires, etc., or tank linings, or multilayer films of 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-1238E (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 top of this, 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 and bonding the sheet, allowing it to stand for 10 seconds, then 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/min) (4) Shear adhesive strength JIS K 6850 (5) Thread cutting test Japan Water Works Association standard JWW AK 132-1982 (Polyethylene powder lined steel pipe for water supply ) stated in
Using a thread cutting method using an SGP-PC pipe machine, measurements were taken while varying the ambient temperature, and the maximum temperature at which thread cutting was possible was measured. (6) Pipe wrench tightening torque test Use a vise and 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), and use a pipe wrench to fix the coating 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) Blend 0.6 parts of maleic anhydride and 0.025 parts of 2,5-dimethyl-2,5-di-(tertiary-butylperoxy)-hexane-3 to 100 parts, mix with a Henschel mixer, and mix this mixture into a 6 mmφ Supply to a single screw extruder and melt-knead at a set temperature of 230℃ and screw rotation speed of 60rpm to modify with maleic anhydride.
Got LLDPE. This modified LLDPE and polyisobutylene [manufactured by Etsu Kagaku Co., Ltd., Vistanecs MML-
80 (product name) unmodified LLDPE and HDPE Table-1
A composition was obtained by blending the ingredients in the proportions shown below and heating, melting and kneading them at 230°C. Using the physical properties of each composition obtained and each composition, a laminate with a steel plate of each preheating temperature was prepared and the peel strength and shear adhesive strength were measured, and the results are shown in Table 1.
It was shown to. For comparison, when LLDPE with MI of 5 g/10 min was used and ethylene butene rubber [manufactured by Mitsui Petrochemical Co., Ltd., A-4085 (trade name)] was used instead of polyisobutylene.
In the case of using EBR (hereinafter referred to as EBR) and the case of not incorporating HDPE, compositions were prepared and laminates were prepared in the same manner as in Example 1, and the physical properties and peel strength were measured, and the results are also listed in Table 1. did.

【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.
The modified polyethylene composition used in was extruded into a tube shape at a resin temperature of 220°C with a thickness of 1 mm and a line speed of 1 m/min using a 65 mmφ extruder, and was cooled in a water tank with a distance of 3 cm from the die to form a resin coating. Obtained steel pipe.
The peel strength and physical properties of the obtained coated steel pipe 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】

[Table] Examples 11 and 12 Unmodified LLDPE and HDPE used in Examples 1 and 4
and polyisobutylene in the proportions shown in Table 3, maleic anhydride and Example 1 were added to this mixture.
A modified polyethylene composition was obtained by reacting in the same manner as above. A laminate with a steel plate was prepared using the obtained composition, and the physical properties and peel strength were 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.
10-90% by weight, (B) unmodified polyethylene (excluding high-density polyethylene) 0-85% by weight, (C) high-density polyethylene and/or reacting the high-density polyethylene with an unsaturated carboxylic acid or its derivative and (D) polyisobutylene and/or 5 to 50% by weight of modified polyisobutylene obtained by reacting the polyisobutylene with an unsaturated carboxylic acid or a derivative thereof.
An adhesive polyethylene composition consisting of.