JPS5845989B2 - adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adhesive composition, and more particularly to an adhesive composition useful for coating a metal steel pipe with a synthetic resin.

Conventionally, metal steel pipes have been coated with synthetic resins, generally polyolefin resins (especially polyethylene and polypropylene), by extrusion methods, thermal spraying methods, etc. for the purpose of protection and corrosion prevention. (abbreviated)).

However, as is well known, polyolefin resin is a chemically stable non-polar polymer, so it has poor adhesion to the surface of steel pipes, and as it is, it cannot sufficiently protect the steel pipes from corrosion.

Therefore, in order to compensate for this, methods have been adopted in which various adhesive materials are applied to the surface of the steel pipe prior to the coating.

In such a coating method, the above-mentioned adhesive material is required to have the following performance characteristics.

(1) A restraining force that prevents the coating polyolefin resin from moving from the tube end due to contraction due to stress relaxation of the polyolefin resin when the coated steel pipe is exposed to high ambient temperatures (for example, left outdoors in the summer). (2) When the coated steel pipe is buried underground or underwater, it has a water-resistant adhesion that prevents peeling between the steel pipe surface and the coating polyolefin resin.

Examples of the above-mentioned adhesive include: (1) an adhesive based on bituminous material, consisting of natural or synthetic rubber, tackifying resin, etc.; (2) a tackifying resin based on ethylene copolymer resin;
Adhesives made of wax and the like are commercially available.

However, all of them have some drawbacks and have not been able to fully satisfy the protection and corrosion prevention functions of coated steel pipes.

Specifically, the above adhesive (■) does not easily cause peeling between the surface of the steel pipe and the coating polyolefin resin even under conditions of underground and underwater use, and has water-resistant adhesion, but when exposed to high ambient temperatures. However, there are disadvantages in that the adhesive softens significantly, loses its binding force on the coating polyolefin resin, and causes the resin to move from the end of the tube.

In addition, with the adhesive described in (■) above, the softening of the adhesive is small even when exposed to high ambient temperatures, and it has a binding force on the coating polyolefin resin. It has the disadvantage that peeling phenomenon easily occurs between the resins and the water-resistant adhesion is poor.

Therefore, it has a binding force that can prevent the coating polyolefin resin from moving from the pipe end even under high ambient temperature conditions, and there is no peeling phenomenon between the steel pipe surface and the coating polyolefin resin even under underground or underwater conditions. There has been a strong desire for the emergence of an adhesive with excellent water-resistant adhesion that is less likely to occur.

As a result of intensive research to provide an adhesive that satisfies such demands, the present inventors have developed a composition containing a liquid polymer obtained by polymerizing petroleum fraction, an ethylene copolymer resin, and an oil-soluble phenolic resin. By focusing on the tackiness of the material and specifying the types (or special values) and proportions of the components, it was discovered that the intended purpose could be achieved, and the present invention was completed.

The gist of the present invention is (a) 10 to 60 parts by weight of a liquid polymer with a molecular weight of 300 to 5,000 obtained by polymerizing C4, C5, and C6 fractions of petroleum components, (b) vinyl acetate content of 5 to 45 parts by weight.
% by weight or ethyl acrylate content 8-20% by weight
5 to 50 parts by weight of an ethylene copolymer resin having a melt index value of 0.5 to 400, and (C) 5 to 50 parts by weight of an oil-soluble phenolic resin having a C5-12 alkyl. A solvent-free adhesive composition for polyolefin resins.

The liquid polymer (a) in the present invention refers to one obtained by polymerizing C4, C5, and C6 fractions of petroleum components, and contributes to softening of the composition of the present invention.

Specific examples include 1,4-cis polybutadiene, 1,2-polybutadiene, and polyisobutylene obtained by polymerizing C4 fraction, and 1,3-polypentadiene and polyisobutylene obtained by polymerizing C5 fraction. Examples include cyclopentadiene and polydimethylbutadiene obtained by polymerizing a C6 fraction, and one or a mixture of two or more of these may be used.

Particularly suitable is 1,3-polypentadiene, which is inexpensive and easily available.

These liquid polymers have a molecular weight of 300~
It is desirable to set it to 5000, preferably 700 to 1100.

If the molecular weight is less than 300, the polymer tends to decompose or scatter into the air during heating during preparation or coating of the composition of the present invention, and if it exceeds 5,000, its softening function tends to decrease. .

The ethylene copolymer resin (b) in the present invention refers to a copolymer resin of ethylene and various polymerizable monomers (vinyl acetate, acrylic esters, methacrylic esters, etc.), and one of these Alternatively, a mixture of two or more types is used.

In particular, ethylene-vinyl acetate copolymer resin and ethylene-vinyl acetate copolymer resin
Ethyl acrylate copolymer resins are preferred.

These ethylene copolymer resins have a melt index (hereinafter abbreviated as MI) value (AST D123).
8 (hereinafter the same) is preferably set to 0.5 to 400, preferably 15 to 300.

If the above MI value is less than 0.5, the hot melt viscosity of the resin will be too high, making it difficult to prepare and apply the composition of the present invention, and if it exceeds 400, the softening point of the composition of the present invention will decrease. □The binding force on the coating polyolefin resin at high ambient temperature is lost.

In addition, in the above-mentioned preferred copolymer resin, the copolymerization ratio is usually such that the vinyl acetate content is 5 in the case of a vinyl acetate type.
It is desirable that the amount is selected to be 45% by weight, preferably 10 to 20% by weight.

If this content is less than 5% by weight, the adhesion of the composition of the present invention to the steel pipe surface will be poor, and if it exceeds 45% by weight, the softening point of the composition of the present invention will decrease, making it difficult to coat at high ambient temperatures. It tends to lose its binding force on polyolefin resins.

In the case of ethyl acrylate, the content of ethyl acrylate is 8 to 20% by weight, preferably 15 to 20% by weight.
It is desirable that the

If this content is less than 8% by weight, the low-temperature properties of the composition of the present invention will deteriorate, and if it exceeds 20% by weight, the softening point of the composition of the present invention will decrease and the coating polyolefin will It tends to lose its binding force on the resin.

The oil-soluble phenol resin (c) in the present invention is, for example, a condensate of formaldehyde and an alkylphenol such as pt-butylphenol, pt-amylphenol, or pt-octylphenol.
Examples include 0% phenol resin and modified products thereof (dry oil modified products, natural resin modified products, etc.), and one type or a mixture of two or more of these can be used.

In particular, oil-soluble phenolic resins having 05 to 12 alkyl groups are suitable.

As mentioned above, the composition of the present invention comprises the above-mentioned essential components (a-
It is characterized by being a solvent-free type containing c), and the blending ratio of each component is particularly important in achieving the initial desired effect of the present invention.

That is, 10 to 60 parts by weight, preferably 20 to 50 parts by weight of liquid polymer (a), ethylene copolymer tree, Qtlb)
It is important to select a ratio of 5 to 50 parts by weight, preferably 10 to 40 parts by weight, and 5 to 50 parts by weight, preferably 10 to 40 parts by weight of the oil-soluble phenol resin.

The proportion of the liquid polymer is less than 10 parts by weight,
The effect of the composition of the present invention as a softener is small, and
If the amount exceeds 1 part by weight, the softening point of the composition of the present invention decreases, and the binding force against the coating polyolefin resin at high ambient temperature decreases.

When the proportion of the ethylene copolymer resin is less than 5 parts by weight, the cohesive force of the composition of the present invention is so small that it does not lose its binding force on the coated polyolefin resin at high ambient temperatures.
If the amount exceeds 50 parts by weight, the viscosity of the composition of the present invention when melted by heat increases, making composition preparation and coating operations difficult.

If the proportion of the oil-soluble phenolic resin is less than 5 parts by weight, the adhesion of the composition of the present invention to the surface of the steel pipe will be reduced and the water-resistant adhesion will be ineffective, and if it exceeds 50 parts by weight, the composition of the present invention will The material becomes pores, the wettability is reduced, and the adhesion to the coating polyolefin resin is reduced.

In addition to the above-mentioned essential components, the composition of the present invention contains attacking polypropylene, fillers, and various other additives (anti-aging agents,
Antioxidants, etc.) may be added in an appropriate amount.

The above-mentioned attack polypropylene has a molecular weight of 100 to 100,000, preferably 3,000 to 1
2000 can be used.

If the molecular weight is less than 1,000, the softening point of the composition of the present invention will be lowered and the binding force for the coating polyolefin resin will not be lost at high ambient temperatures, and if it exceeds 100,000, the hot melt viscosity will be too high and the composition will Preparation and application operations become difficult.

The amount to be added is usually selected within the range of 5 to 20% by weight based on the total amount of the above essential components, from the viewpoint of water resistant adhesion improvement effect and compatibility.

Examples of the filler include aluminum oxide, antimony oxide, asbestos, barium carbonate, barium sulfate, bentonite, kaolin, magnesium oxide, magnesium carbonate, calcium carbonate, sericite, silica, talc, titanium oxide, and calcium sulfate.

Among these, talc is particularly suitable because it is inexpensive, has a relatively small increase in hot solvent viscosity, is excellent in composition preparation and coating work, and is effective in improving water-resistant adhesion.

The amount added is usually 20% of the total amount of the above essential components, from the viewpoint of improving water resistant adhesion and workability during composition preparation and application.
It may be selected within the range of 50% by weight.

In preparing the composition of the present invention, the above-mentioned essential components are blended in a predetermined ratio, the various additives mentioned above are mixed in as needed, and the mixture is heated all at once using a hot mixer, hot kneader, etc. Just use the melting temperature line.

The temperature for heating and melting is usually 140 to 220°C.
1. Preferably, the temperature is in the range of 150 to 200°C.

The composition thus prepared is uniformly applied to the surface of a metal steel pipe by a hot-melt coating method under heating and melting, and then a prescribed polyolefin resin is coated thereon by an extrusion method, a thermal spraying method, etc. Then, by cooling to room temperature, a coated steel pipe with a desired degree of adhesion and high performance can be obtained.

If the composition of the present invention, which has the above-mentioned structure, is used for making coated steel pipes, it will not only maintain initial adhesion but also excellent water-resistant adhesion and sufficient binding force against the coating polyolefin resin at high ambient temperatures. becomes possible.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Examples 1 to 4 (1) Preparation of adhesive composition: The ingredients shown in Table 1 (parts by weight) were mixed at once with a hot mixer at a heating melting temperature of 160 to 170°C for 1 hour to form an adhesive composition. Prepare agent compositions (, &1 to 4).

Various properties of such compositions are shown in Table 2.

(2) Preparation of coated steel pipe: The adhesive composition prepared above was heated and melted again and applied to the outer surface of a metal steel pipe with an outer diameter of 50 mm to a thickness of 0.3 mm using a hot melt coating method. Density polyethylene is coated by extrusion, and then cooled to room temperature to produce a synthetic resin-coated steel pipe.

(3) Performance testing of coated steel pipes: A shear strength test to measure the initial adhesion force, a temperature gradient test to measure the restraint force on the coated polyethylene at high ambient temperature, and a surfactant aqueous solution immersion test to measure the water-resistant adhesion force are as follows. The test results are shown in Table 3.

Shear strength test A cut is made on the coated steel pipe to reach the surface of the steel pipe, and 1010X
A test agent having a test area of 10 is prepared, and the adhesion force (kg/crA) is measured using a Tensilon tensile tester UTM-3 (tensile speed 200 mm 1 m 1 n, measurement temperature 20°C or 60°C).

Temperature gradient test A coated steel pipe is immersed in hot water at 70°C for 1 hour, taken out, and then left at room temperature (20°C) for 1 hour.

This immersion → leaving is considered as one cycle, and when this cycle is repeated 5 times, the distance traveled by the coated polyethylene from the pipe end (
mm).

Surfactant aqueous solution immersion test A cut with a width of 1011 tr/L reaching the steel pipe surface was made on the coated steel pipe, and this was soaked in a 1% nonionic surfactant aqueous solution.
After being immersed in a test tank maintained at 0° C. for 96 hours, the presence or absence of a peeling phenomenon at the cut portion of the taken out coated steel pipe was determined with the naked eye.

Comparative Examples 1 and 2 A commercially available adhesive is prepared using the following ingredients and in the same manner as in the examples.

Various properties of such agents are shown in Table 2.

* Next, using the two types of commercially available adhesives prepared above, a synthetic resin-coated steel pipe was created under the same conditions and method as in the example, and then a performance test of the coated steel pipe was conducted.

The test results are shown in Table 3.

The adhesive composition of Example 1 uses an ethylene-vinyl acetate copolymer resin in an ethylene copolymer resin, and is a compound with excellent adhesion to metals, and the adhesive composition of Example 2 uses an ethylene-vinyl acetate copolymer resin. It is a compound that uses ethyl acrylate copolymer resin and has excellent thermal stability.
In Example 3, an ethylene-vinyl acetate copolymer resin and an ethylene-ethyl acrylate copolymer resin were used in combination, which is a standard formulation that harmonizes the properties of each, and in Example 4, These formulations are made inexpensive by mixing appropriate amounts of attack polypropylene and fillers, and as is clear from Table 3 above, both have good restraint on the coated polyethylene at high ambient temperatures. Moreover, it is recognized that it has excellent water-resistant adhesion.

Comparative Examples 3 and 4 Using the ingredients (parts by weight) shown in Table 4, pressure-sensitive adhesive compositions having the properties shown in Table 4 are prepared in the same manner as in Examples.

Using this composition, a synthetic resin-coated steel pipe was prepared under the same conditions and method as in the examples, and then a performance test of the coated steel pipe was conducted.

The test results are shown in the same table.

If the composition of the present invention lacks some of the essential components, it may not be usable as an adhesive, or even if it can be used, it may have poor binding force to the coated polyethylene at high ambient temperatures, or may have poor water resistance. Adhesion is poor.

Claims (1)

[Scope of Claims] 1(a) 10 to 60 parts by weight of a liquid polymer with a molecular weight of 300 to 5,000 obtained by polymerizing C4, C5, and C6 fractions of petroleum components, (b) Vinyl acetate content of 5 to 45 parts by weight % or ethyl acrylate content of 8 to 20% by weight and a melt index value of 0.5 to 400 ethylene copolymer resin 5 to 50
1. A solvent-free pressure-sensitive adhesive composition for a metal-polyolefin resin, comprising: parts by weight, and (c) 5 to 50 parts by weight of an oil-soluble Fe, Nor resin having an alkyl group of C5 to C12.