JPH02229811A - Production of heat resistant vinyl chloride based copolymer resin - Google Patents

Abstract

PURPOSE:To obtain the title resin having excellent transparency and heat resistance and suitable for pipe, sheet, container, etc., by adding N-arylmaleimide to vinyl chloride, copolymerizing vinyl chloride with N-arylmaleimide and extracting and removing a low-molecular weight material from the resultant copolymer by an organic solvent. CONSTITUTION:N-Arylmaleimide (e.g. N-phenylmaleimide) is separately or continuously added to vinyl chloride and copolymerized with vinyl chloride and a low-molecular weight material is extracted and removed from the resultant copolymer so as to keep an extraction amount from the resultant copolymer to >=0.1wt.% by an organic solvent to provide the aimed resin. Furthermore, extraction and removal of the low-molecular weight material by the organic solvent is preferably carried out e.g. by dissolving the copolymer in an organic solvent such as THF or acetone capable of dissolving the copolymer and dropwise adding the solution to an organic solvent such as methanol incapable of dissolving the copolymer to deposit the copolymer and filtering the deposited copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a heat-resistant vinyl chloride copolymer resin. (Prior art) Polyvinyl chloride resin has mechanical strength, weather resistance, self-extinguishing properties, and chemical resistance. It has excellent properties and is widely used for thermoforming into pipes, plates, films, sheets, containers, etc. However, polyvinyl chloride resin has a low softening point and poor heat resistance. For example, it softens and undergoes thermal deformation at 70 to 80°C, so it cannot be used at higher temperatures. As a method to improve the heat resistance of polyvinyl chloride resin,
For example, Japanese Patent Publication No. 41-9551 proposes a method of copolymerizing vinyl chloride with an N-arylmaleimide such as N-phenylmaleimide.

However, since N-arylmaleimide has a different copolymerizability ratio with vinyl chloride, if all N-arylmaleimide is added at once during copolymerization,
The vinyl chloride copolymer obtained is a mixture of those with a high content of N-arylmaleimide and those with a low content. Therefore, transparency is poor and heat resistance does not improve much. (Problems to be Solved by the Invention) Therefore, the present inventor has developed a method using vinyl chloride as a main component and adding N to it.
- When copolymerizing N-arylmaleimide such as phenylmaleimide, attempts have been made to add N-arylmaleimide to vinyl chloride in portions or to add it continuously for copolymerization. As a result, it was found that a copolymer with a relatively uniform composition was obtained, and its transparency and heat resistance were improved. However, the copolymer obtained in this way has poor thermal stability (and even if it is thermoformed with an organotin stabilizer that has excellent transparency and thermal stability, the resulting molded product turns yellow). There is a problem with coloring.

The present invention is intended to solve the above problems, and its purpose is to provide a method for producing a heat-resistant vinyl chloride copolymer resin that is transparent and has excellent thermal stability and heat resistance.

(Means for Solving the Problems) The present inventor has discovered that the cause of coloring due to heat is a low molecular weight vinyl chloride-N-arylmaleimide copolymer formed as a by-product during copolymerization, and that such a low molecular weight copolymer is We obtained the knowledge that it is easy to oxidize and cause dehydrochlorination. The present invention was made based on this knowledge.

The method for producing a heat-resistant vinyl chloride-based copolymer resin of the present invention consists of using vinyl chloride as a main component and copolymerizing N-arylmaleimide therewith, by adding the N-arylmaleimide in portions to the vinyl chloride, or It is characterized by continuously adding and copolymerizing, extracting and removing low molecular weight substances from the obtained copolymer with an organic solvent, and reducing the amount extracted from the obtained copolymer to 0.1% by weight or less, This achieves the above objectives. In the present invention, the N-arylmaleimide to be copolymerized with vinyl chloride is a substituted or unsubstituted aromatic maleimide, such as N-phenylmaleimide, N (
0, Il+P)-chlorophenylmaleimide, N-(o
．． w,p) monomethylphenylmaleimide, N-(o
．． ts. p) monomethoxyphenylmaleimide, N
(0,lI+p) monoethylphenylmaleimide, N
- (o, m, p) monoethoxyphenylmaleimide, N - (o, peng, p) monohydroxyphenyl maleimide, N - (o, m, p) ~ carboxyphenyl maleimide, N - (o, m, p )-12trophenylmaleimide, N-(o+ Ill, p)-cyanophenylmaleimide, N-(o,n+,p)-tert-butylphenylmaleimide, N-2,6-dichlorophenylmaleimide, N-2 .6-'; ethyl phenyl malemide, N
-p-diphenylmaleimide, N-α-naphthylmaleimide, N-βnaphthylmaleimide, and the like.

To copolymerize vinyl chloride with N-arylmaleimide, suspension polymerization, emulsion polymerization, and solution polymerization are generally employed. In particular, the suspension polymerization method is preferably employed because the obtained copolymer is relatively free of impurities and the manufacturing cost is relatively low.

Specifically, suspension polymerization is carried out by the following method. First, in a jacketed pressure-resistant polymerization vessel equipped with a stirrer, water such as ion-exchanged water, partially saponified polyvinyl alcohol, a methyl cellulose derivative, a suspension stabilizer such as sodium polyacrylate, and tert-butyl baroxy A radical polymerization initiator such as neodecanoate, penzoyl peroxide, and azobisisobutyronitrile is added and stirred. Next, after removing the air inside the polymerization vessel, vinyl chloride is injected. Thereafter, the temperature inside the polymerization vessel is raised to a predetermined temperature by heating from the jacket to start polymerization.

Then, during the progress of the polymerization reaction, a predetermined amount of N-arylmaleimide is added in portions or continuously.

The N-arylmaleimide is added after being dissolved in a suitable solvent such as acetone or methanol, or dispersed in water. The amount of N-arylmaleimide added is such that the content of the N-arylmaleimide component in the resulting copolymer is 1
The content of the vinyl chloride component is adjusted to be 55 to 99% by weight.If the N-arylmaleimide component is less than 1% by weight, the improvement in heat resistance will be small;
If it exceeds 0% by weight, heat resistance will improve, but fluidity during molding will decrease.

Preferably, the addition of N-arylmaleimide is continued until 80% by weight or more of the vinyl chloride is polymerized. The polymerization temperature is generally 30 DEG to 90 DEG C., and the polymerization time is generally 2 to 20 hours. After copolymerization is carried out at a predetermined temperature for a predetermined time, the remaining vinyl chloride monomer is discharged outside the vessel to obtain a slurry copolymer, which is dehydrated and dried to obtain a powder copolymer. Manufacture.

The thus obtained copolymer is subjected to extraction and removal of low molecular weight substances using a 1i' solvent. As a specific method for extracting and removing low molecular weight substances using an organic solvent, for example, the copolymer is dissolved in a certain amount of an organic solvent that dissolves the copolymer, such as tetrahydrofuran, acetone, or cyclohexanone, and this solution is The copolymer is precipitated by dropping it into a certain amount of an organic solvent such as methanol that does not dissolve the copolymer while stirring, and then filtering it to remove only low molecular weight substances such as low molecular weight copolymers. A method of removing it is adopted.

In addition, an organic solvent that swells the copolymer, or an organic solvent that swells the copolymer by mixing a solvent that dissolves the copolymer and a solvent that does not dissolve the copolymer, and swells the copolymer using such an organic solvent. A method of removing only low molecular weight substances such as low molecular weight copolymers as a solution is also adopted.

In this way, low molecular weight copolymers in the copolymer are removed. At this time, the above-mentioned organic solvent is used to extract and remove low molecular weight substances so that the amount extracted from the resulting copolymer is 0.1% by weight or less. Here, the amount extracted from the above copolymer is 100 ml of a mixed solvent of 1 volume of tetrahydrofuran and 4 volumes of methanol! This value was measured by adding 10 g of the copolymer to the solution, stirring at 30° C. for 4 hours to swell the copolymer, filtering it, and evaporating the filtrate to dryness. If the amount extracted from the obtained copolymer is more than 0.1% by weight, the extraction and removal of low molecular weight substances will be insufficient and the effect of the present invention will be reduced.

In addition, during the above copolymerization, other monomers copolymerizable with vinyl chloride may be added as necessary.
For example, to increase heat resistance, styrene, α-methylstyrene, vinylidene chloride, methyl methacrylate, acrylonitrile, etc. are used, and to improve fluidity during molding, ethylene, propylene, etc. α-olefins, vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether,
Acrylic acid esters are used. Such monomers are preferably added in a range that does not impair the original properties of the vinyl chloride resin, for example, in a range of 30 weight percent or less. In this way, a heat-resistant vinyl chloride copolymer resin is obtained. When manufacturing molded objects such as pipes, plates, and containers using this copolymer resin, polyvinyl chloride resin is generally used as a heat stabilizer, lubricant, plasticizer, antistatic agent, pigment, filler, etc. The compounding agents used in the above are added as necessary.

(Function) In the present invention, a vinyl chloride-N-arylmaleimide copolymer having a uniform composition can be obtained by adding N-arylmaleimide to vinyl chloride in portions or continuously adding it and copolymerizing it. This improves transparency and heat resistance. In addition, low molecular weight substances such as low molecular weight vinyl chloride-N-arylmaleimide copolymers that are easily thermally oxidized are removed from the obtained copolymer by solvent extraction, thereby improving thermal stability. (Example) Examples and comparative examples of the present invention will be shown below.

A pressure-resistant polymerization vessel with a jacket equipped with a stirrer for 25 f of soil per application,
Ion exchange water 12f, partially saponified polyvinyl alcohol 7
．． After charging 14.4 g of 2 g s tart-butyl baroxyneodecanoate and sealing the reactor to remove remaining air, 3.6 kg of vinyl chloride was injected and heated to 50° C. from the jacket of the polymerization reactor.

Immediately after the temperature inside the vessel reached 50"C, a solution of 26.8g of N-phenylmaleimide dissolved in 41.5g of acetone was added as one dose, and this was added at 5 minute intervals for 40"C.
It was press-fitted into the polymerization vessel several times.

Thereafter, residual vinyl chloride was removed from the vessel, and the slurry was taken out and washed with ion-exchanged water to remove suspension stabilizers and the like, and dehydrated and dried.

The copolymer thus obtained was dissolved in 5 times the amount of tetrahydrofuran, and 20 times the amount of methanol was added dropwise with stirring to precipitate the copolymer, which was filtered and dried and N
- A vinyl chloride-N-phenylmaleimide copolymer containing a phenylmaleimide component of 30% by weight was obtained.

When the substance obtained by evaporating the above filtrate to dryness was examined using an infrared absorption analyzer, it was confirmed that it was a vinyl chloride-N-phenylmaleimide copolymer. Also,
When the molecular weight of this copolymer was measured by gel permeation chromatography, the number average molecular weight was 4200, which was a low molecular weight with a degree of polymerization of about 80. The amount of extraction, heat resistance, thermal stability, and transparency of the obtained copolymer were measured by the following measuring methods. The results are shown in Table 1.

(1) Extraction amount Add 10 g of the copolymer to 100 d of a mixed solvent of 1 volume of tetrahydrofuran and 4 volumes of methanol, stir at a temperature of 30°C for 4 hours to swell the copolymer, and filter it. The filtrate was evaporated to dryness and the weight of the extract was determined and expressed as weight percent relative to the copolymer.

(2) 100 parts by weight of a heat-resistant copolymer, 2.5 parts by weight of dimethyltin merkabute and 0.3 parts by weight of wax (Kaoh-8
This mixed powder was kneaded with a 190°C roll to create a sheet, and the sheets were stacked and kneaded in a press kept at 190°C for 5 minutes.
Heat and pressurize at 75kg/c+a for 6.4-minutes.
A molded plate was created. Using this molded plate, ASTM
The deflection temperature, which is an index of heat resistance, was measured according to O-648. (3) Thermal Stability and Transparency A molded plate with a thickness of 1-10 mm made in the same manner as above was tested using a 45° diffusion color converter (SM-4-C, manufactured by Suga Test Instruments Co., Ltd.). To measure the degree of yellowing and total light transmittance, which are indicators of thermal stability and transparency, the measurement temperature was 20°C).

Jengketsu 1 In Example 1, the solvent extraction treatment was carried out by putting the copolymer in a mixed solvent of 5 times the amount of acetone and 20 times the amount of methanol, and stirring at 30 ° C for 4 hours to swell the copolymer. The same procedure as in Example 1 was carried out except that the method was changed to a method of obtaining a copolymer by filtration and drying. The results are shown in Table 1.

In Example 1, 26.8 g of N-phenylmaleimide
The same procedure as in Example 1 was carried out except that 26.8 g of No-chlorophenylmaleimide was used. The results are shown in Table 1. In Example 1, 26.8 g of N-phenylmaleimide
The same procedure as in Example 1 was conducted except that 41.5 g of acetone was replaced with 40.2 g of N-2.6-diethylphenylmaleimide and 62.2 g of acetone.

The results are shown in Table 1.

For comparison, in Example 1, instead of adding N-phenylmaleimide in portions, 1070% of N-arylmaleimide was added before polymerization.
Example 1 was carried out in the same manner as in Example 1, except that g was charged into the polymerization vessel all at once. The results are shown in Table 1.

Comparison Example 1 The same procedure as in Example 1 was conducted except that no solvent extraction treatment was performed. The results are shown in Table 1.

And Ainuki 1 In Example 1, the solvent extraction process was changed to a method in which the copolymer was placed in 25 times the volume of methanol, stirred at 30°C for 4 hours, and then filtered and dried to obtain the copolymer. Except for this, the same procedure as in Example 1 was carried out. The results are shown in Table 1. Northern comparison 1 {The same procedure as in Example 3 was performed except that no solvent extraction treatment was performed. The results are shown in Table 1.

Comparison Example 4 was carried out in the same manner as in Example 4, except that no solvent extraction treatment was performed.

The results are shown in Table 1.

(Left below) (Effects of the invention) As mentioned above, when copolymerizing N-arylmaleimide with vinyl chloride as the main component, N-arylmaleimide is added to the vinyl chloride in portions or continuously. By adding and copolymerizing, a heat-resistant vinyl chloride copolymer resin with excellent transparency and heat resistance can be obtained. A heat-resistant vinyl chloride copolymer resin with excellent thermal stability can be obtained by extracting and removing such low molecular weight substances and reducing the amount extracted from the copolymer to 0.1% or less. Therefore, the heat-resistant vinyl chloride copolymer resin obtained by the method of the present invention can be suitably used in applications requiring heat-resistant transparency, such as pipes, plates, and containers.

Claims (1)

[Claims] 1. When vinyl chloride is the main component and N-arylmaleimide is copolymerized with vinyl chloride, the N-arylmaleimide is added to the vinyl chloride in portions or continuously and copolymerized. A method for producing a heat-resistant vinyl chloride copolymer resin, which comprises extracting and removing low molecular weight substances from a polymer using an organic solvent, and controlling the amount extracted from the resulting copolymer to 0.1% by weight or less.