JPS6131445A - Resin composition - Google Patents

Abstract

PURPOSE:A resin composition for extrusion lamination, showing improved adhesiveness to various substrates, having little smell, and improved heat sealability, comprising a specific ethylenic terpolymer and an olefinic copolymer. CONSTITUTION:(A) A terpolymer having preferably 1-15, especially 5-10 melt index, comprising ethylene, 0.8-5mol%, preferably 1.5-3mol% alkyl (meth)acrylate, and 0.15-1.5mol%, preferably 0.6-1.2mol% maleic anhydride is blended with (B) a copolymer of an olefin and 2-30mol%, preferably 3-15mol% hydroxyl group-containing vinyl monomer, such as saponified ethylene vinyl acetate copolymer in a blending ratio of 1/10-1/2 equivalent, preferably 1/5-1/3 equivalent hydroxyl group of the component B based on number of mol of maleic anhydride of the component A in a molten state.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a resin composition for extrusion lamination.

(Prior Art) Conventionally, polyolefin polymers, particularly low density polyethylene, are often used as resins suitable for extrusion lamination. Low-density polyethylene has various excellent physical properties as an extrusion laminate, but because the resin is inherently non-polar, it has poor adhesion to substrates such as paper, aluminum, polyester, and cellophane. In order to provide sufficient 1 for adhesion, it is possible to oxidize and activate the surface of the film by molding at a very high temperature (300-340°C), but even this is not sufficient, and molding at too high a temperature is possible. This accelerates thermal deterioration, leading to problems such as reduced formability and smoke smells, so when laminating to a base material such as aluminum, a type of adhesive called an anchor coating agent is usually applied to the base material. Lamination is required, which complicates the process and poses problems in the working environment.

In order to cover these weaknesses of low density polyethylene,
Ethylene-based copolymers of the lip type are sometimes used for extrusion laminates.

Typical examples include a copolymer of ethylene and an unsaturated carboxylic acid in which part of the carboxylic acid is neutralized and crosslinked with ions such as zinc, or a copolymer of ethylene and acrylic acid.

These copolymers have good moldability and excellent heat sealing performance, making them suitable for extrusion laminates.
Furthermore, it exhibits good adhesion to certain types of base materials such as aluminum when molded at low temperatures (300° C. or lower). However, adhesive strength is not necessarily sufficient for various plastics such as polyester, cellophane, and stretched polypropylene, and it is difficult to directly obtain strong adhesive strength with extrusion laminate I.

In addition, other copolymers include terpolymers of ethylene-alkyl (meth)arylate and pyrohydric maleic acid, and this polymer is widely used for paper, aluminum, and various plastic materials. It is known to exhibit good adhesion. However, in order to obtain sufficient adhesion, 0.
It is necessary to introduce 8 mo1% or more of maleic anhydride.

Such polymers have low melt tension and are unsuitable as resins for extrusion laminates. That is, although the melt drawability during molding is sufficient, it has the drawback of extremely large neck-in.

Furthermore, due to the influence of unreacted maleic anhydride and alkyl (meth)acrylate remaining in the polymer, or various compounds generated due to these during molding, the odor is strong, making it especially difficult to use in materials such as food packaging. There is a big problem.

(Problems to be solved by the invention) Considering these circumstances, we have developed a material that has sufficient adhesive strength to various base materials without the need for an anchor coating agent, and has moldability odor at the same level as conventional low-density polyethylene. As a result of research into resins for extrusion laminates that can maintain the properties of the resin, the following composition was found to be suitable for such purposes, leading to the present invention.

The resin composition exhibits good adhesion to various substrates, has little odor, and has good heat-sealing properties, so it can be widely used as a heat-seal layer or as a sand layer without an anchor coating agent in various extrusion laminates. can.

(Means for solving the problem) The ethylene terpolymer (A) used in the present invention is an alkyl (meth)acrylate having the structure of ethylene and (I), (
It is a ternary copolymer of maleic anhydride represented by II), in which R1 in (I) represents hydrogen or a methyl group, and R2 represents an alkyl group having 1 to 8 carbon atoms. Specific examples include methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, and M12-ethylhexyl acrylate. (I) and (II) occupying in the polymer
) ratios are 0.8-5 molX and 0.15-5 molX, respectively.
1.5mo 1% better is Sohtsure 1.5~3n+
oL%, 0. fi ˜1.2 malt. If the amount of alkyl (meth)acrylate is less than 0.8z, maleic anhydride cannot be introduced for a sufficient period of time, so adhesion cannot be sufficiently exhibited, and heat sealability is also poor, resulting in insufficient lamination suitability. When it is 5% or more, it becomes difficult to increase the molecular weight and crystallinity of the polymer, and neck-in becomes too severe. The ratio of maleic anhydride is 0.1
If it is less than 5X, the polarity will be insufficient and sufficient adhesiveness will not be obtained.

If it is more than 1.5%, the polymer production technique will be strained and the polymer cannot be produced stably, and the absorption of moisture in the air by maleic anhydride will increase, causing foaming during molding. I don't like it.

In addition, the polymer melt index (JIS-878
0) is not particularly limited, but is preferably 1-15, particularly 5-IO, in order to perform appropriate extrusion lamination.

As a method for producing the copolymer, a high-pressure method and low-density polyethylene polymerization equipment can be used. For example, maleic anhydride and alkyl (meth)acrylate at a temperature of 170 to 280'C and a pressure of 1.000 to 2,000 kg.
/cm'' into the reactor together with ethylene,
Polymerization is carried out by injection of a free radical initiator such as t-butyl peroxypivalate, t-butyl peroxy 2-ethylhexanoate, di-t-butyl peroxide, and the like.

After lowering the pressure, the produced polymer and unreacted monomer are separated, and the polymer is turned into pellets through an extruder.

Propylene, butane, butene,
It is also possible to add several hundred ppm to several percent of a phenolic compound such as 2.5-di-t-butylhydroxytoluene as a molecular weight regulator such as acetin, or as a reaction stabilizer. be.

As the copolymer (B) of an olefin and a vinyl monomer containing a hydroxyl group, a copolymer of ethylene and vinyl alcohol units, a copolymer of ethylene and hydroxyalkyl (meth)acrylate, etc. can be used. As an example of the former, a saponified product of ethylene vinyl acetate copolymer is effective, and this polymer can be easily produced. The latter uses a high-pressure low-density polyethylene plant to produce, for example, hydroxyethyl methacrylate, similar to the terpolymer described above.
What is necessary is to produce a copolymer of 1. and ethylene. In addition to the above-mentioned components, the copolymer (B) can contain other comonomers within a range that does not impair the object of the present invention. At this time, the proportion of monomer units containing hydroxyl groups in the polymer is 2 to 30 mol%, preferably 3 to 30 mol%.
It is 15 mol%. If this proportion is less than 2 mol%, -OH
Since the absolute state of the group is small, a large amount of polymer is required to be added, and the ratio of ethylene-alkyl (meth)acrylate to maleic anhydride terpolymer is relatively reduced, leading to poor adhesion. .

Moreover, if it exceeds 30 mol %, the dispersion of -OH groups becomes insufficient, a non-uniform crosslinking reaction occurs, and a gel is generated in the film.

The resin composition for extrusion lamination according to the present invention is produced by, for example, melt-mixing the two types of copolymers described above, and the method used is the same as the method used when kneading ordinary polyolefin polymers. It can be used. That is, Banbury mixers, rolls, extruders of various types, and the like. The mixing ratio of the two types of copolymers is 1/1 with respect to the number of moles of maleic anhydride in the maleic anhydride-based terpolymer (A).
0 to 1/2 mole of j□1, preferably 115 to 173
The copolymer (
Adjust the ratio of B). If this molar ratio is less than 171O, the number of hydroxyl groups that react with maleic anhydride will be insufficient and the neck-in will not be sufficiently improved, and it will not be more than 1/2.
- On the other hand, the reaction progresses too much and the fluidity of the resin worsens.
In addition to deteriorating moldability and productivity due to decreased melt drawability,
As the amount of maleic anhydride is reduced, adhesion to each substrate is reduced.

Laminate molding is carried out using a resin composition produced under the following conditions. The molding temperature is determined by the required adhesive strength and neck-in, but is usually 260 to 300°.
C is appropriate.

The maleic anhydride in the ternary copolymer and the hydroxyl group in the olefin copolymer are not catalyzed, and in such a dilute state, they can be mixed slowly at temperatures above 250°C with considerable kneading. It is thought that as the reaction progresses, the terpolymer becomes partially crosslinked through the hydroxyl groups, the melt tension increases significantly, and the neck-in decreases.

However, the degree of crosslinking expressed by the gel fraction is
- It is preferable to keep the content to 10% or less, preferably 1% or less so as not to adversely affect the appearance etc. Here, the gel fraction is determined by placing the polymer sample in a 300-mesh wire mesh and
After Soxhlet extraction with boiling xylene, the weight was measured after drying in the wire mesh at 80° C. for 16 hours, and the weight remaining in the wire mesh was calculated and expressed in percentage.

Additionally, since this reaction also occurs with unreacted maleic anhydride or low molecular weight substances containing maleic anhydride, it also plays a role in fixing unreacted substances in the polymer, which was previously the main cause of odor. Since the low molecular weight substances are significantly reduced, the odor of the product is greatly improved, and it can be used without worry even in fields where odor is a concern, such as food applications. If it is necessary to further reduce the odor, further reduction in odor can be achieved by using an antioxidant widely used in polyolefin resins.

(Example) 1 Arashi 1 The ethylene-methacrymethymethyl-maleic anhydride terpolymer is a copolymer of ethylene and vinyl alcohol units produced using a high-pressure low-density polyethylene production plant. Saponified product of ethylene-vinyl acetate copolymer (vinyl acetate content 30 weight 2) (saponification degree 85%)
It was used. In addition, the quantitative determination of each monomer in the copolymer was determined by using an infrared absorption spectrum and elemental analysis.

Using a 50-mass extruder, the two types of copolymers mentioned above were
The mixture was melted and mixed at 150°C, pelletized, and coated on various substrates using a laminate molding machine, and various physical properties were measured.

The extrusion lamination conditions are as follows (same in the following examples). Melt stretchability was measured by gradually increasing the take-up speed at an extruder rotation speed of 30 mpm until the melt film became unstable. The withdrawal speed was measured. The adhesive strength was measured by cutting the sample laminated on each base material in the direction of take-up with a width of 1.5cm, and conditioning the sample at 23°C and 50% humidity for 24 hours. A speed gouging test was conducted.The results are shown in Table 1.

As is clear from the results in the table, the polymer mixture has low neck-in, good moldability and odor, and also exhibits good adhesion to various substrates and can be molded well without the need for an anchor coating agent. I found out something.

EXAMPLE 1 The following measurements were carried out in the same manner as in Example 1, except that an ethylene ethyl acrylate-maleic anhydride terpolymer was used as the ethylene-based terpolymer shown in Table 1.

The results are shown in Table 1.

As a monomer containing a hydroxyl group, methacrylic acid 2-
A copolymer of hydroxyethyl and ethylene was produced using hydroxyethyl. Polymerization was carried out using a two-piece autoclave reactor at a temperature of 200° C. and a pressure of 1800 kg/cm′ in the same manner as in Example 1 except that a copolymer having the above composition was used. The results are shown in Table 1.

The ethylene-methacrymethymethyl-maleic anhydride pentacopolymer used in Example 1.3 was subjected to a laminate test alone. Although the adhesive strength to each base material was strong and lamination was possible without an anchor coating agent, the neck-in was large and the moldability and productivity were poor. That is, the thickness of the laminate cannot be made uniform, and both edges become thick, resulting in a large amount of product loss, poor productivity, and a very strong odor, making it unsuitable for applications such as food packaging materials.

Comparison 1 A lamination test was conducted on ethylene-acrylic acid copolymer. It had good moldability and showed good adhesion to aluminum base materials and paper base materials, but the adhesive strength was weak to polyester, stretched polypropylene, and cellophane plastic base materials, making it difficult to use anchor coating agents. If laminated without one, the applications will be limited.

Claims (1)

[Scope of Claims] (A) an ethylene terpolymer consisting of ethylene, alkyl (meth)acrylate and maleic anhydride; and (B) an olefin copolymer of an olefin and a vinyl monomer containing a hydroxyl group. A resin composition for extrusion lamination characterized by consisting of a polymer (provided that the mixing ratio of (A) and (B) is such that the number of hydroxyl groups in the (B) copolymer is such that the number of hydroxyl groups in the (A) copolymer is The mixing ratio is such that it is in the range of 1/10 to 1/2 molar equivalent to maleic anhydride)