JPS6043374B2 - Vinyl chloride resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vinyl chloride resin composition that has excellent processability and provides a soft molded article with extremely low compression set.

Vinyl chloride resin generally has excellent chemical and physical properties, and when mixed with a plasticizer, it has appropriate elasticity and can be made into flexible molded products, so it can be used for films, sheets, tubes, containers, etc. It is widely used as a resin raw material for various molded products.

However, soft vinyl chloride resin molded products have the disadvantage of poor creep properties and poor restorability (large compression set) when stress is removed. For example, a soft molded product obtained by blending a plasticizer with a generally widely used vinyl chloride resin having an average degree of polymerization of 1000 to 1300 has a compression set (conditions: 70°C x 2 hours) measured based on JIS 6301. , 25% compression) is extremely large at 60 to 70%, which limits its use in applications that require small compression set, such as packing.

It is known that the compression set can be improved to some extent by using a vinyl chloride resin with a higher degree of polymerization, but even in the case of a vinyl chloride resin with an average degree of polymerization of 2000 to 3000, the compression set is still 55 to 3000. As large as 60%,
It is not enough to expand its application field.

If a vinyl chloride resin with an average degree of polymerization of 8,000 or more or more than 10,000 is used, it is possible to reduce the compression set to 50% or less, but if a vinyl chloride resin with such a high degree of polymerization is used, the price will only increase. First, the processability becomes extremely poor, making it impractical. On the other hand, an attempt was made to obtain soft molded products with low compression set by using a gel-containing vinyl chloride resin obtained by adding a polyfunctional compound such as diallyl phthalate to the polymerization system during the polymerization of vinyl chloride. has been proposed, but the improvement in compression set is not so great, and such gel-containing vinyl chloride resins have the drawback of being much worse in processability than general-purpose vinyl chloride resins. As a result of intensive studies on this technical problem, the present inventors have developed a crosslinked vinyl chloride copolymer obtained by adding an oligomer having an ethylenic double bond to the polymerization system during the polymerization of vinyl chloride. The present invention was completed based on the discovery that by using the resin, a vinyl chloride resin composition can be obtained which exhibits moldability comparable to that of general-purpose vinyl chloride resins, while having significantly improved compression set.

That is, the present invention provides (a) vinyl chloride containing crosslinks in the molecule obtained by copolymerizing a vinyl chloride monomer and an oligomer having at least two ethylenic double bonds in one molecule; system copolymer resin 10 to 9 parts by weight,
(b) 90 to 1 part by weight of a vinyl chloride resin that does not substantially contain crosslinks in the molecule, and (c)
The present invention relates to a vinyl chloride resin composition comprising a necessary amount of plasticizer.

To explain this, when vinyl chloride monomer is copolymerized with an oligomer having an ethylenic double bond, the resulting copolymer tends to have a low degree of polymerization, and it is necessary to copolymerize to obtain a high degree of polymerization. Even if polymerization occurs, at most i=2000~25(4
), and when using the usual polymerization method to obtain general-purpose vinyl chloride resin, i = 300 to 100.
It will be about 0. A higher degree of polymerization is desirable for the purpose of improving compression set, but it is difficult to obtain a copolymer resin with a high degree of polymerization, and it also causes a significant increase in cost. However, by using (a) ordinary vinyl chloride resin in combination with this copolymer resin,
It is possible to obtain molded products with extremely low compression set, which is impossible to obtain with general-purpose vinyl chloride resin alone.
Further, there is an advantage that the molding processability at that time is also good.

(b) To obtain the copolymer resin as a component, when vinyl chloride is subjected to suspension polymerization to obtain a polymer, an oligomer having at least two ethylenic double bonds in one molecule is added to the polymerization system. It is sufficient if the amount is present in a fixed amount, and as a result, a vinyl chloride copolymer resin containing crosslinked bonds in the molecule can be obtained.

The oligomer used at this time is required to have two or more ethylenic double bonds in one molecule in order to introduce crosslinks into the molecules of the copolymer to be produced, and The degree is generally in the range of 10 to 100. Monomers that serve as raw materials for such oligomers include diolefins such as butadiene and isoprene, aromatic vinyl compounds such as styrene and α-methylstyrene, acrylic acid, methyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate. Examples include acrylic acid derivatives such as methacrylic acid, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, olefins such as ethylene and propylene, acrylonitrile, etc., but when the monomer is an acrylic acid derivative, The number of carbon atoms is 4 to “1”
2. In the case of methacrylic acid derivatives, it is preferable to use those having 5 to 12 carbon atoms.

Oligomers can be obtained from these monomers by conventionally known methods.

In this case, the above-mentioned aromatic vinyl compound, acrylic acid derivative, or methacrylic acid derivative may be used alone or in combination of two or more thereof, and in the case of this combination, the proportion of each component to be used is determined according to the amount obtained. There are no particular limitations on the oligomer as long as it can be suitably used in the present invention. (a) When producing the component, the oligomer may be used in an amount of 0.5 to 5 parts by weight per 10 parts of the vinyl chloride monomer, and the crosslinked vinyl chloride copolymer resin obtained in this way When insoluble matter in tetrahydrofuran (25°C) is measured, it is approximately 40-10% by weight.
It is.

Next, the vinyl chloride resin as a (mouth) component is a resin that does not substantially contain crosslinks in the molecule, and is a resin that contains ordinary general-purpose vinyl chloride resin or vinyl chloride and other monomers such as acrylic ester and methacrylic acid. Included are esters, vinyl esters, vinyl ethers, olefins, vinylidene halides, and copolymers with styrene, acrylonitrile, maleic anhydride, and the like.

In the present invention, the (mouth) component has an average degree of polymerization of 1000 or more, preferably 2000 or more, more preferably 3000 or more.
A product with a high degree of polymerization as described above is desirable.

The composition of the (a) component and the (mouth) component is determined by the degree of polymerization of each component,
The preferred ratio is determined by the amount of component (a) insoluble in tetrahydrofuran, etc., but in particular, the average degree of polymerization of the component dissolved in tetrahydrofuran (25°C) in the mixture should be 3000 or more, and the insoluble content should be 30 to 7. It is desirable to have a mixture that satisfies the saliva amount %.

In order to achieve the above-mentioned conditions, the distribution ratio of both components should be 10 to 9 parts by volume of the (a) component and 90 parts by volume of the (mouth) component.
It is necessary to make it 1 part by weight, especially 30 parts of component (A).
It is desirable that the (mouth) component be 70 to 3 parts by weight for 7 parts by weight.

When obtaining a molded article using the resin composition of the present invention, (c) a plasticizer is used, and this plasticizer may be one that has been conventionally used for manufacturing flexible molded articles of vinyl chloride resin. Any of these may be used, including phthalate esters, aliphatic dibasic acid esters, glycol esters, fatty acid esters, phosphate esters, citric acid ester plasticizers, as well as epoxy plasticizers, polyester plasticizers, Examples include urethane plasticizers.

The blending amount is determined by the type of molded product, the field of application, etc., and is generally 50 PHR or more, preferably 70 PHR.
R or more is preferable. In addition, stabilizers, lubricants,
As in the past, fillers and other various additives may be added.

Next, reference examples and examples will be given and explained. Reference example (
Production of crosslinked vinyl chloride copolymer resins) The components shown in Table 1 were charged into a 5' autoclave, and polymerization was carried out at a predetermined polymerization temperature to obtain crosslinked copolymer resins 1 to 2.

About this copolymer resin Tetrahydrofuran (THF)
The average degree of polymerization of the insoluble matter and the TlIF' dissolved matter was measured. The THF-insoluble content is calculated by dividing 1.00g of the sample to be measured into 10
After dissolving in 0ml of THF and shaking for 60 minutes at the boiling point of THF and centrifuging the undissolved matter, 20ml of the supernatant solution was added.
ml was placed in a beaker and evaporated to dryness at 105°C, and 5 times the weight was taken as the THF soluble content.
The value obtained by subtracting the F soluble content was defined as the L positive non-soluble content.

The average degree of polymerization of the η normal solution was calculated from the viscosity value at 30° C. of a 0.4% solution of nitrobenzene obtained by evaporating the THF solution to dryness at 100° C. according to JIS K672l.
Example: Polyvinyl chloride, a plasticizer (DOP), a stabilizer (Ba
-Zn system) was mixed, placed on a mixing roll heated to 175°C, wound around the roll, and kneaded for one round.

When the roll winding time during kneading and the compression set of the molded product were measured, the results shown in each table were obtained. Average degree of polymerization of the L-positive and THF-soluble components of the mixed resin composition: Average degree of polymerization of the THF-insoluble components and THF-soluble components of the crosslinked copolymer resin, polyvinyl chloride (
Each value of the average degree of polymerization (THF insoluble content 0%) is weighted averaged according to the mixing ratio of both, and the T of each mixed resin composition is
The average degree of polymerization was taken as the average degree of polymerization of the HF-insoluble portion and the L-positively soluble portion.

Measurement of roll winding time: The time (in seconds) from when the mixture was put on the roll until the mixture appeared to be in a gelled state on the roll surface was measured using a stopwatch.

Measurement of compression set: Based on JISK63Ol, measured under the conditions of 70°C x n hours and 25% compression, test piece creation conditions...1
85℃ preheating 7 minutes, 30k9/CTI pressurization 4 minutes (1) TH
Influence of F-insoluble content As shown in Table 2, in order to keep the compression set to 50% or less, it is necessary to contain 30% or more of THF-insoluble content.

On the other hand, if the undissolved content is 70% or more, the compression set will improve and the roll winding time will become longer. (2) Effect of the mixing ratio of crosslinked copolymer resin and polyvinyl chloride As shown in Table 3, When compared with the case without, by blending polyvinyl chloride with an average degree of polymerization of 3800, the compression set increases by about 10%,
Roll winding time can be reduced by 40-60%.

E) Effect of the average degree of polymerization of the THF soluble content As shown in Table 4, when looking at the effect of the average degree of polymerization of the THF soluble content for TFIF' insoluble content of 45%, the compression set is 50%. % or less, the average degree of polymerization is 30
If the average degree of polymerization is 5000 or more, the compression set will be 45% or less.

1) Influence of crosslinking (THF-insoluble content) generation method As shown in Table 5, when diallylphthalate is used as a crosslinking copolymerization component (comparative example) and polybutadiene (molecular weight 2000), compression set and roll winding time are respectively T
When compared with the same average degree of polymerization for the lIF-insoluble content and the L-positive soluble content, the present invention is superior in terms of compression set, and in particular, it is significantly superior in processability.

Claims (1)

[Scope of Claims] 1 (a) A crosslinked vinyl chloride copolymer resin obtained by copolymerizing a vinyl chloride monomer and an oligomer having at least two ethylenic double bonds in one molecule. 10 to 90 parts by weight, (b) 90 to 10 parts by weight of a vinyl chloride resin containing substantially no crosslinks in the molecule, and (c) a necessary amount of a plasticizer. 2. The vinyl chloride resin composition according to claim 1, wherein the component (b) has an average degree of polymerization of 3000 or more.