JPH05320434A - Prevention of degradation of polyolefinic resin - Google Patents

Abstract

PURPOSE:To prevent the degradation in mechanical properties, discoloration, etc., of a polyolefin resin by compounding it with a specific high-molecular compd. CONSTITUTION:A polyolefinic resin is compounded with a high-molecular compd. contg. 5-90% structural units of CH2CH(OH) as a degradation preventive in such an amt. that the content of the units in the resulting compsn. is 0.1-30-wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prevention of deterioration of polyolefin resins.

[0002]

2. Description of the Related Art Polyolefin resins are closely related to life as inexpensive general-purpose resins. It has a wide range of uses, and is widely used for agriculture, household products, containers, packaging materials, building materials, and the like. However, when a plastic molded product such as an agricultural vinyl sheet is used outdoors for a long period of time, deterioration mainly occurs due to the action of the ultraviolet rays of sunlight. Since such deterioration causes discoloration and deterioration of mechanical properties, various deterioration preventing agents have been added to prevent the deterioration. The conventional anti-deterioration agents are roughly classified into two types, that is, an antioxidant and a light stabilizer, in view of their functions.

The action of antioxidants is mainly classified into the following three types. That is, inhibition of radical chain reaction, decomposition of peroxide, and removal of heavy metals. Further, the light stabilizer has a function of absorbing ultraviolet rays and not giving energy to the polymer. That is, it prevents the energy of ultraviolet rays from directly acting on the molecular chain to break the bond and cause deterioration. Since conventional deterioration inhibitors have low molecular weight, they may not be compatible with high molecular weight polyolefin polymers or blended polymers, and their form is often in powder or liquid form. It is often necessary to use a special method or to go through several steps in order to reach a good mixed state by kneading with the polymer.

When the compatibility between the deterioration preventing agent and the resin is not good, the resin is dissolved and mixed in an organic solvent such as toluene or benzene, or mixed by utilizing the point of being soluble in a monomer such as styrene monomer. There were things. The standard addition amount is 0.1 to 1% by weight with respect to the resin, but if the compatibility is not good, the dispersibility deteriorates. Therefore, it is necessary to use a dispersant or improve the dispersibility. Therefore, it was necessary to add a large amount. However, when the addition amount is large, generally the mechanical properties of the molded product are deteriorated, or in the case of an agricultural film or the like, it is necessary to pass ultraviolet rays well, whereas the addition of a large amount of a light stabilizer is required. Will interfere with the original purpose of the product. In addition, the deterioration inhibitor generally has a conjugated cyclic unsaturated bond or a heavy metal in its structure and is colored. Therefore, if added in a large amount, the molded product is colored, which is not preferable.

[0005]

Since the deterioration inhibitors that have hitherto been used have a low molecular weight, they have a low compatibility with the polymer material polyolefin and require a complicated operation when mixed with the polyolefin. However, a large amount of addition was required to exert the deterioration preventing effect. However, addition of a large amount of deterioration inhibitor causes various problems as described above.
Therefore, the present invention can effectively prevent the deterioration of the polyolefin resin, is easy to add and mix with the polyolefin, and the addition causes deterioration of mechanical properties and quality such as coloring. It is an object of the present invention to provide an anti-deterioration agent that does not deteriorate

[0006]

In order to solve such a problem, the present inventors have found that the compatibility with the polyolefin is controlled so that the addition amount does not adversely affect the polyolefin to be added. Based on the idea that a polymer material should be used as a deterioration inhibitor that satisfies the conditions that it is good, easy to add and mix before or during molding, and that there is no risk of coloring due to addition, we proceeded with the study, Invented. That is, the inventors have found that a polymer compound having a —CH ₂ —CH (OH) — structural unit, such as an ethylene-vinyl alcohol copolymer, is suitable as the polymer material satisfying the above conditions. I found it. There has never been an example of using a polymer material to prevent deterioration of plastic.

The gist of the present invention is --CH ₂ --CH (OH).
A deterioration preventive agent for a polyolefin resin, which is composed of a polymer compound containing a structural unit of-. The present invention also provides a method for preventing deterioration by adding the above-mentioned deterioration inhibitor to a polyolefin resin so that the structural unit of —CH ₂ —CH (OH) — becomes 0.01 to 30% by weight based on the total amount of the resin composition. Concerned.

This high molecular weight anti-deterioration agent has an excellent anti-deterioration effect on the polyolefin resin, and has good compatibility with the polyolefin and good dispersibility, so that it can be easily added and mixed and can be easily molded. In addition, there is an advantage that the molded product is not colored by addition and the mechanical properties are not deteriorated. Further, when the melting point of this deterioration inhibitor is not largely different from that of the polyolefin, it is advantageous in melt mixing and molding. A molded article made of a polyolefin resin to which such a deterioration inhibitor is added can effectively suppress and prevent the progress of deterioration even during long-term outdoor use.

[0009]

The present invention will be described in detail below. The polyolefin resin targeted for deterioration prevention in the present invention is a resin composition composed of a simple substance resin of polyolefin or a mixture of two or more kinds of polyolefins. Examples of the polyolefin resin include polyolefin homopolymers and olefin copolymers, and specifically, polyethylene, polypropylene, poly-1-butene, polyisobutylene, poly-1.
Examples thereof include pentene and ethylene-vinyl acetate copolymer. Of these, resins having a branched structure such as polypropylene are susceptible to deterioration, and the addition of the deterioration inhibitor of the present invention is particularly effective.

The deterioration preventive agent of the present invention is --CH ₂ --CH.
A polymer compound containing a (OH)-structural unit (hereinafter sometimes referred to as a vinyl alcohol structural unit), for example, an ethylene-vinyl alcohol copolymer obtained by completely saponifying an ethylene-vinyl acetate copolymer. Polymer,
An ethylene-vinyl alcohol-vinyl acetate copolymer obtained by partially saponifying an ethylene-vinyl acetate copolymer,
Examples thereof include vinyl alcohol-vinyl acetate copolymers obtained by partially saponifying polyvinyl acetate. However, -C
A polymer compound consisting only of H ₂ —CH (OH) — structural units, that is, a polyvinyl alcohol simple substance, is not suitable because of its poor compatibility with polyolefin, its water solubility, and its high moisture permeability. The deterioration preventing agent of the present invention is -CH ₂
The --CH (OH)-structural unit is preferably contained in the range of 5 to 90%, more preferably 5 to 70%.

A preferred deterioration inhibitor is a polymer compound represented by the following general formula.

[0012]

[Chemical 1]

In the above general formula, each structural unit is randomly arranged, and the number of each structural unit is as follows. When x is 0: If y + z = 1, 0.05 <y <0.7,
0.3 <z <0.95, when x is not 0: When x + y + z = 1, 0.3 ≦ x ≦ 0.95, 0.05 ≦ y <0.7 The above copolymer usually has a molecular weight in the range of several thousand to several hundred thousand. When a partially saponified copolymer is used, the mechanical properties can be adjusted by the content of vinyl acetate. For example, when the content of vinyl acetate is 20% or more, the softening point is lowered to make the composition viscous and also has a plasticizing effect. In addition, the melting point of the above-exemplified copolymer does not have a great difference from the melting point of the polyolefin, so that the melt mixing and molding with the polyolefin are extremely easy.

The deterioration preventing action of the deterioration preventing agent of the present invention will be described below. Polyolefin resins such as polyethylene and polypropylene have a relatively large amount of oxygen permeation, and oxygen molecules easily permeate into the resin molded product. For this reason, oxygen molecules are excited by ultraviolet energy or thermal energy and the radicals generated in the molecular chain generate oxygen molecules, which reduces the mechanical properties of the molded product.

The polymer compound containing a vinyl alcohol structural unit used in the present invention has a very small oxygen permeation amount (for example, an ethylene-vinyl alcohol copolymer is 0.5% by weight).
(cc / m ² · 24Hr · atm)], the addition of this acts to reduce the oxygen permeation amount of the polyolefin molded product. In this way, the amount of oxygen molecules, which is the cause of deterioration, is drastically reduced from that in the resin molded product, so that the progress of deterioration can be suppressed.

Further, since the polymer compound containing the vinyl alcohol structural unit has a hydroxyl group in the side chain, even if a radical causing deterioration is generated in the molecular chain, it is trapped and a chain reaction is caused. It can be prevented from occurring and consequently deterioration can be suppressed.

As described above, the deterioration preventive agent of the present invention has an excellent deterioration preventing effect and has good compatibility with polyolefin, so that the deterioration can be effectively prevented even with a small addition amount. It is also possible to add a large amount in order to enhance the effect of suppressing deterioration. This is because addition of a large amount does not cause coloration of the molded article, and since it is a high-molecular compound with good compatibility, it does not cause a decrease in mechanical properties due to a large amount of addition.
When the same deterioration inhibitor is used, the larger the amount added, the greater the effect of suppressing deterioration. Since the addition amount in a wide range is possible in this manner, the deterioration preventing effect of the molded product can be adjusted by the addition amount to adjust the life outdoors, for example.

The deterioration preventive agent of the present invention contains --CH ₂ --CH (OH)-structural units in an amount of 0.1 to 30 relative to the total amount of the resin composition.
It is preferable to add it in such an amount that it becomes wt%. Adjusting the amount of the deterioration inhibitor added to the polyolefin-based polymer depending on the content of the --CH ₂ --CH (OH)-structural unit in the deterioration inhibitor to change the mechanical properties of the resulting molded article. Is also possible. For example, when the content of the vinyl alcohol structural unit in the deterioration inhibitor is 10% by weight, the deterioration inhibitor may be added in a large amount of about 50% by weight based on the total amount of the resin composition. Also, when adding a deterioration inhibitor having a high content of vinyl alcohol structural units, the addition amount may be small relative to the total amount of the composition, so that it is not desired to alter the mechanical properties of the base polyolefin resin. Suitable for various applications. In this way, the resin composition according to the application can be obtained by adjusting the addition amount of the deterioration inhibitor according to the content of the vinyl alcohol structural unit in the deterioration inhibitor. However, considering the compatibility with the polyolefin resin, it is preferable that the content of the vinyl alcohol structural unit is in the range of 0.05 to 20% by weight with respect to the total amount of the molded product.

The deterioration inhibitor may be added in advance before molding the polyolefin resin or may be mixed during molding. Furthermore, other conventional additives may be added. Molding of the resin composition containing the deterioration inhibitor of the present invention is a conventional method for molding a polyolefin resin,
It can be performed using a molding machine. For example, various shapes such as extrusion molding, compression molding, injection molding, blow molding, and vacuum molding can be used to mold into any shape such as block, film, powder, and tube. It can be applied to various uses similar to conventional polyolefin resins, but it can be advantageously used especially for outdoor use and in vinyl sheets for agricultural use, etc., where transparency and light-transparency of molded products are required.

[0020]

【Example】

[0021]

Example 1 Commercially available polyethylene (MI = 2, melting point 118
Ethylene-vinyl alcohol copolymer (MI = 1.5, melting point 162 ℃, density 1.19) with a vinyl alcohol structural unit content of 50 mol% for pellets with a temperature of ℃ and a density of 0.925 g / cm ³ )
g / cm ³ ) 10% by weight of pellets are added and mixed (the content of vinyl alcohol structural unit is 5% by weight with respect to the total amount of the resin composition), and the temperature range is 170 to 220 ° C while uniaxially mixing Heated to pellet. 180 to 240
Extruded with a T-die in the temperature range of ℃, film thickness 20μ
Got a film of m.

[0022]

Comparative Example 1 Commercially available polyethylene alone (MI = 2, melting point 1
A film having a thickness of 20 μm was formed under the same conditions as in Example 1 at 18 ° C. and a density of 0.925 g / cm ³ ). Each of the films obtained in Example 1 and Comparative Example 1 was cut into a sheet of 7 cm × 12 cm, which was measured by a sunshine arc weather meter (black panel temperature 35 ° C., rainfall / sunny weather = 12/60 minutes).
An acceleration test was performed for 250 hours, and mechanical properties and weight average molecular weights were measured and compared. The results are shown in Tables 1 and 2. Table 1 shows the change in tensile elongation in the exposure test, and Table 2 shows the change in the weight average molecular weight in the exposure test.

[0023]

[Table 1]

[0024]

[Table 2]

In Comparative Example 1, the elongation rate decreased 200 hours after the start of exposure and became about 1/2 after 250 hours. The decrease in molecular weight is also remarkable. On the other hand, in Example 1, even after 250 hours, the elongation rate was reduced by 10%, and the molecular weight was hardly reduced, indicating that the progress of deterioration was suppressed.

[0026]

Example 2 Commercial polyethylene (MI = 2, melting point 118
Polyethylene (MI = 2, melting point 150 ° C, density 0.918 g / cm ³ ) 60% by weight, vinyl alcohol structural unit content 50 mol% ethylene-vinyl based on pellets of ℃, density 0.925 g / cm ³ ). Alcohol copolymer (MI = 1.5, melting point 1
Pellets having a temperature of 62 ° C. and a density of 1.19 g / cm ³ ) were added and mixed in an amount of 1% by weight (additional amount of vinyl alcohol structural unit was 0.5% by weight based on the total amount of the resin composition), and the mixture was molded into a film under the same conditions as in Example 1. ..

[0027]

Comparative Example 2 Commercially available polyethylene (MI = 2, melting point 118
Polypropylene (MI = 2, melting point 150 ° C., density 0.918 g / cm ³ ) was added and mixed at a ratio of 60% by weight to pellets having a temperature of 0.925 g / cm ³ and the mixture was mixed in the same manner as in Example 1. It was formed into a film. The films obtained in Example 2 and Comparative Example 2 were each cut into a sheet of 7 cm × 12 cm, and the sunshine arc weather meter (black panel temperature
A 200 hour accelerated test was performed at 35 ° C and rainfall / sunny weather = 12/60 minutes), and the mechanical properties and weight average molecular weight were measured and compared. The results are shown in Tables 3 and 4. Table 3 shows the change in tensile elongation in the exposure test, and Table 4 shows the change in the weight average molecular weight in the exposure test.

[0028]

[Table 3]

[0029]

[Table 4]

At 200 hours after the start of the exposure, cracks were generated in Comparative Example 2, whereas no cracks were generated in Example 2. Also, the decrease in the molecular weight after 200 hours is reduced to about 50,000 which is about 1/10 of that before exposure in Comparative Example 2, but is about 200,000 in Example 2, and the decrease in molecular weight due to deterioration is suppressed. It is clear that

[0031]

According to the present invention, by adding a polymer compound containing a vinyl alcohol structural unit to a polyolefin resin, it is possible to suppress the progress of deterioration of a molded article,
The life of the molded product can be extended when the molded product is used outdoors. The deterioration preventing agent used in the present invention is a polymer material unlike conventional ones, so that it has good compatibility with polyolefin resins, can be easily mixed and molded, and has a high deterioration preventing effect even when added in a small amount. Therefore, it is possible to provide a polyolefin resin molded article having excellent quality without deterioration of mechanical properties and coloring of the molded article. Also, this deterioration inhibitor is
The addition amount can be adjusted by the content of the polyvinyl alcohol structural unit, and thus a resin composition having desirable mechanical properties depending on the application can be obtained.

Claims (2)

[Claims] 1. A deterioration inhibitor for a polyolefin resin, comprising a polymer compound containing a structural unit of —CH ₂ —CH (OH) —. 2. The deterioration preventing agent according to claim 1 is added to the polyolefin resin so that the structural unit of —CH ₂ —CH (OH) — becomes 0.01 to 30% by weight with respect to the total amount of the resin composition. A method for preventing deterioration of a polyolefin-based resin, which comprises adding the same.