JPH06172410A - Production of ethylene-vinyl chloride copolymer and its composition - Google Patents

Abstract

PURPOSE:To produce a nontoxic molded body excellent in thermal stability and plasticizer absorbability without any fish eye by carrying out the suspension copolymerization of vinyl chloride with ethylene in the presence of an oil-soluble polymerization initiator and a specific dispersion stabilizer. CONSTITUTION:The suspension copolymerization of a mixture of vinyl chloride with ethylene and other copolymerizable monomers is carried out in the presence of an oil-soluble polymerization initiator and a dispersion stabilizer to produce a copolymer having 0.1-25wt.% ethylene composition and 75-99.9wt.% vinyl chloride composition. In the process, a partially saponified polyvinyl alcohol having 70-90mol% saponification degree and 1500-3000 average polymerization degree and a partially saponified polyvinyl alcohol having 70-90mol% saponification degree and 300-1000 average polymerization degree as a dispersion stabilizer, a secondary dispersion stabilizer and a water-soluble cellulosic ester are used in combination. A partially saponified polyvinyl alcohol having 20-65mol% saponification degree and 100-1000 average polymerization degree is used as the secondary dispersion stabilizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and composition for producing an ethylene-vinyl chloride copolymer, and more particularly to a method for producing an ethylene-vinyl chloride copolymer having excellent heat stability and less fish eyes, and The present invention relates to a composition of ethylene-vinyl chloride copolymer capable of obtaining a molded article which is substantially non-toxic.

[0002]

2. Description of the Related Art Ethylene-vinyl chloride copolymer (hereinafter referred to as
Ethylene PVC) is used in various fields because it has excellent physical and mechanical properties and excellent primary and secondary processability derived from the internal plasticizing effect of ethylene. However, vinyl chloride polymer (hereinafter,
It has the drawback of being inferior in thermal stability to PVC).

Generally, PVC is used in combination with various stabilizers for the purpose of suppressing decomposition during molding and processing. A typical stabilizer system, a composite metal soap stabilizer, is used for food packaging containers and medical applications. It is preferably used in applications requiring non-toxicity such as instruments and pharmaceutical packaging containers, and in applications requiring severe non-toxic regulation of lead elution amount such as water pipes and joints. In that case, a compound for promoting the effect of the stabilizer (hereinafter referred to as “stabilizing aid”) may be used in combination, and examples of such stabilizing aid include polyols and / or their esters, phosphites, and epoxies. Compounds and the like have been heretofore known, and are used in the compounding and kneading steps prior to PVC production or processing.

Ethylene PVC is used in sheets, films, plates, tubes, and many other fields because of its excellent workability, but by taking advantage of its excellent secondary formability, it is formed into a sheet by vacuum forming, drum forming, or the like. It is also often used as a food packaging container, a pharmaceutical packaging container, a shrink film for packaging drinking water bottles that require stretching, and a secondary processing tube. As mentioned above, these applications are fields that are required to be non-toxic, and there has been a demand for improving the thermal stability when a complex metal soap-based stabilizer is used for ethylene PVC. .

To meet these requirements, ethylene PVC
In the case of improving the thermal stability by adding the above-mentioned stabilizing aid at the time of the production of the above, it is possible to batch, divide, or continuously before the start of the polymerization and / or after the start of the polymerization and before the termination. In the case of adding, as a result of lowering the dispersion stabilizer of the monomer mixture, ethylene PVC may not be obtained, or the uniformity of the particles of the obtained ethylene PVC may be lowered, and fish eye may increase. Ethylene PVC with increased fish eyes is not suitable for food packaging applications, pharmaceutical packaging applications, and secondary processing pipes. Sheets for food packaging and pharmaceutical packaging, and packaging containers molded from the sheets are P
This is the most severe appearance product of the products obtained from VC, and an increase in fish eyes significantly reduces the value of the product, which is not preferable. Further, usually, the secondary processing pipe is a PVC pipe obtained by extrusion molding (primary processing),
It can be obtained by subjecting it to secondary processing such as blow molding or sleeve processing after heating, but the fish eyes present in the primary processing tube may deteriorate the appearance of the final product or destroy the tube during secondary processing. The increase of fish eyes is not preferable because it causes a decrease in product yield due to the reasons such as the connection.

In addition, when the above-mentioned stabilizing aid is added during the production of ethylene PVC, when it is added after the termination of polymerization, and when an insoluble compound is added to the monomer mixture, ethylene PVC is added. The transparency, which is an important feature of the molded product using, is unfavorable because the fish eyes increase, and even when a soluble additive is used in the monomer mixture, the transparency may decrease. is there. Ethylene PV
C is produced by suspension polymerization using PVA, a water-soluble cellulose ether, and a surfactant, which are known as general dispersion stabilizers for suspension polymerization of PVC, and PVA is classified into the above-mentioned polyols. It also has an effect as a stabilizing aid. 47, No. 6, p
p. 509 (June, 1990) and the like.

However, when PVA is used for the purpose of improving the thermal stability of ethylene PVC and is used in the mixing and kneading steps, PVA having a high degree of saponification is used.
(In particular, PVA having a saponification degree of 70 mol% or more) may have poor compatibility with ethylene PVC, resulting in a decrease in transparency of the molded product, or a decrease in mechanical strength due to poor dispersion. When PVA having a low saponification degree is used,
As a result of using a large amount because of its poor ability as a stabilizing aid,
It can cause the same problems as highly saponified PVA.

On the other hand, when PVA is used as the dispersion stabilizer during the suspension polymerization of ethylene PVC, the compatibility with ethylene PVC is improved by the graft polymerization of the monomer mixture with PVA, resulting in a decrease in transparency. However, when a large amount of PVA is used for better thermal stability, the dispersion stability of the monomer mixture decreases and ethylene PVC is obtained. Or the resulting ethylene PVC has reduced plasticizer absorbability, fish eyes, and residual vinyl chloride levels, resulting in unsatisfactory compositions and molded articles. Another problem arises.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing ethylene PVC having high heat stability and plasticizer absorbability and good fish eye characteristics, and a composition thereof. .

[0010]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the inventors of the present invention have carried out suspension polymerization in an aqueous medium to obtain an ethylene composition of 0.1 to 25% by weight and a vinyl chloride composition. In the method for producing ethylene PVC of 75 to 99.9% by weight, it was found that an ethylene PVC having good properties can be obtained by using a specific combination of PVA and cellulose as a dispersion stabilizer,
Further, they have found that a composition having good properties can be obtained by mixing the obtained ethylene PVC with a composite metal soap-based stabilizer, and completed the present invention.

That is, in the present invention, a mixture of ethylene and vinyl chloride monomers as essential components and other copolymerizable monomers is suspended in an aqueous medium in the presence of an oil-soluble initiator and a dispersion stabilizer. In the method for producing ethylene PVC having an ethylene composition of 0.1 to 25% by weight and a vinyl chloride composition of 75 to 99.9% by polymerization, as the dispersion stabilizer,
(A) Saponification degree is 70 to 90 mol% and average degree of polymerization is 1
PVA of 500 to 3000, (B) saponification degree of 70 to 9
PVA having 0 mol% and an average degree of polymerization of 300 to 1000,
(C) A secondary dispersion stabilizer and (D) a water-soluble cellulose ether are used together, which is a method for producing ethylene PVC.

The present invention will be described in detail below.

Oil-soluble PV as the secondary dispersion stabilizer (C)
When A is used, the total amount of the dispersion stabilizers (A) to (C) used in the present invention is 0.065 parts by weight or more and 1.6 parts by weight, based on 100 parts by weight of the monomer mixture. The amount is preferably the following or more preferably 0.1 part by weight or more and 0.3 part by weight or less. By setting it in this range, a further sufficient thermal stability improving effect is obtained, the transparency of the final molded article is excellent, and the fish eye of the obtained polymer,
The residual monomer level is also excellent.

Further, dispersion stabilizers (A), (B),
The preferable ranges of the amounts of (C) and (D) used are defined by the weight ratio of the respective amounts used.

That is, the weight ratio of (A) :( B) is 1:
It is preferably 2-1: 15. When the amount of (B) is less than twice the amount of (A), the fish eyes, the amount of plasticizer absorbed and the residual vinyl chloride monomer level are poor, and when it is more than 15 times the dispersion stability of the monomer mixture is poor. The polymer particles may not be obtained, or the obtained particles may be coarse.

The weight ratio of (B) :( C) is 5: 1 to.
It is preferably 20: 1, and when (C) is more than one-fifth the amount of (B), a step of recovering unreacted vinyl chloride monomer and removing unreacted vinyl chloride In a process or the like, foaming may occur. On the other hand, when the amount is less than 1/20, the obtained polymer may have poor fish eyes, plasticizer absorbability and residual monomer level.

When a surfactant is used as the secondary dispersion stabilizer (C), the dispersion stabilizer (A) used in the present invention.
The total amount of (B) to (B) is preferably 0.1 part by weight or more and 1.5 parts by weight or less, more preferably 0.1 part by weight or more and 0.1 part by weight or less, based on 100 parts by weight of the monomer mixture. If the amount is less than 3 parts by weight and less than 0.1 parts by weight, sufficient thermal stability improving effect may not be obtained, and if it exceeds 1.5 parts by weight, the transparency of the final molded article may be deteriorated. Or the resulting polymer may have poor fish eyes and poor residual monomer levels.

Further, the amount of the surfactant used is 0.05 parts by weight or more and 2.0 parts by weight or less, and if the amount is less than 0.05 parts by weight, the fish eye, the amount of plasticizer absorbed, and the residual vinyl chloride monomer level are inferior. When the amount exceeds 2.0 parts by weight, fine particles increase in the resulting polymer particles,
It may be difficult to handle the powder, and the hue of the molded product may be reduced.

The dispersion stabilizer (D) is a water-soluble cellulose ether, and any known water-soluble cellulose ether such as methyl cellulose and hydroxypropyl cellulose can be used, but hydroxypropyl methyl cellulose is preferably used. Further, it is desirable to use hydroxypropylmethyl cellulose having a hydroxypropoxyl group substitution degree of 0.15 to 0.25 and a methoxyl group substitution degree of 1.4 to 1.9.

The preferred amount of the water-soluble cellulose ether (D) used is (A) in a weight ratio with the dispersion stabilizer (A):
(D) is 1: 1 to 1: 5. If the amount is more than the same amount as in (A), the resulting polymer particles will contain many fine particles, which may make it difficult to handle the powder.
When the amount is less than the double amount, the dispersion stability of the monomer mixture is poor and polymer particles cannot be obtained, or the obtained particles tend to be coarse.

The above-mentioned dispersion stabilizer may be used by adding the entire amount thereof to the polymerization system before the initiation of the polymerization, and may be added in a divided or continuous manner after the initiation of the polymerization and before the termination of the polymerization. Although it may be used as a mixture, or may be added and used after the termination of the polymerization and before the dehydration of the slurry, it is preferably added and used all at once before the start of the polymerization.

In the present invention, a molecular weight adjusting agent may be used in combination, and the molecular weight adjusting agent used here is
For example, 2-mercaptoethanol having a mercapto group and a hydroxyl group and / or a carboxyl group, 3
-Mercaptopropanol, 4-mercaptobutanol, thioglycerin, thiopropylene glycol, thioacetic acid and the like are exemplified. Of these, 2-mercaptoethanol is preferably used. Other copolymerizable monomers other than ethylene and vinyl chloride used in the present invention include vinyl acetate such as vinyl acetate and vinyl propionate, acrylic ester such as methyl acrylate and ethyl acrylate, or methacrylic ester. ,
Examples thereof include olefins such as propylene, maleic anhydride, acrylonitrile, styrene, vinylidene chloride, and the like, and these may be used as a mixture.

The oil-soluble polymerization initiator used in the present invention is not particularly limited, but examples thereof include percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate and diethoxyethyl peroxydicarbonate. Perester compounds such as t-butyl peroxy neodecaneate, α-cumyl peroxy neodecaneate and t-butyl peroxy neodecaneate; peroxides such as acetylcyclohexyl sulfonyl peroxide: azobis-2.4- Dimethylvaleronitrile, azobis- (4-methoxy-2.
Azo compounds such as 4-dimethylvaleronitrile); further, hydrogen peroxide, etc., which may be used alone or in combination with 2
It is also possible to use a combination of two or more species.

The surfactant used in the present invention may be any of nonionic, cationic and anionic surfactants, such as polyoxyethylene alkyl ester, polyoxyethylene alkyl ether, and polyoxyethylene allyl. Nonionic surfactants such as ethers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, polyoxyethylene and polyoxypropylene block copolymers, glycerin fatty acid esters, polysiloxane polyoxyalkylene block copolymers, polyoxyethylene alkylamines Agents; cationic surfactants such as aromatic ammonium salts, alkyl amine salts, quaternary ammonium salts, alkyl imidazoline quaternary salts; alkyl sulfonates, alkyl There are anionic surfactants such as ryl sulfonates, alkyl phosphates, polyoxyethylene alkyl phosphates, polyoxyethylene alkyl allyl sulfonates, which may be used alone or in combination of two or more. The hydrophilic-hydrophobic balance needs to be 15 or less. If it exceeds 15, only particles having poor fish eyes, plasticizer absorption, and residual monomer level may be obtained. The preferred amount of the surfactant used is 0.05 to 2.0 parts by weight. If the amount is less than 0.05 parts, the amount of fisheye, the amount of plasticizer absorbed, and the residual monomer level are insufficient, and the amount is 2.0 parts by weight. If the amount exceeds the limit, the transparency may decrease.

The method for producing ethylene PVC of the present invention is not particularly limited, and it is carried out under the conditions of known suspension polymerization.

For example, the amount of the aqueous medium used per monomer mixture, the amount of the polymerization initiator, the polymerization temperature, the pressure, the shape of the stirring blade, the stirring speed, the reaction heat removal method, etc. The range that is conventionally adopted may be sufficient. Also, if necessary, known protective colloids, pH adjusters, scale adhesion preventives and the like may be used as long as they do not affect the effects of the present invention. Furthermore, the pressure that rises with the progress of polymerization may be maintained at a constant pressure by withdrawing the monomer mixture from the reaction vessel, or may be allowed to rise within the pressure resistance of the reaction vessel.

In the method of mixing the polymer thus obtained and the complex metal soap-based stabilizer to obtain a composition, the complex metal soap-containing stabilizer used is an organic acid salt of zinc and an alkali metal. And / or a combination with an organic acid salt of an alkaline earth metal may be used, and as the kind of metal,
Examples thereof include lithium, sodium, potassium, magnesium, and calcium, and among them, a combination of calcium and zinc is preferable. Examples of the organic acid include, but are not limited to, carboxylic acids such as formic acid, acetic acid, propionic acid, caprylic acid, lauric acid, palmitic acid, and stearic acid. Also, phosphites, epoxy compounds, polyols such as dipentaerythritol and their derivatives, antioxidants, zeolite,
Stabilizing aids such as perchlorates, processing aids, plasticizers, lubricants,
The use of additives such as pigments, fillers, organotin-based stabilizers, and resins other than vinyl chloride-based resins in combination is acceptable as long as it does not affect the effects of the present invention.

[0028]

EXAMPLES The production method and composition of the present invention will be described below based on Examples and Comparative Examples, but the present invention is not limited thereto.

The following physical properties were measured by the following methods.

(Amount of plasticizer absorbed) German Industrial Standard (DI
N) From 53417/1.

(Thermal stability) When the maximum torque was reached after 60 g of the following composition was added under the conditions of a mixer rotation speed of 60 rpm and a chamber temperature of 160 ° C. using a Brabender Plastograph tester. The thermal decomposition time was defined as the time difference from (a) to the point (b) at which the torque started to rise again due to the decomposition of the resin after the state where the torque decreased and a constant torque was exhibited. Pyrolysis time (HDT, minutes) = (b)-(a) (Adjustment of composition) Vinyl chloride resin 100 parts by weight Di-2-ethylhexyl phthalate 3 parts by weight Epoxidized soybean oil 3 parts by weight Stearic acid 0.2 parts by weight Ca-Zn composite metal soap-based stabilizer 2 parts by weight After weighing out at least 2 parts, 120 ° C using an Ishikawa type stirring and crushing machine
Mix for 10 minutes to obtain the composition.

(Fish Eye) Vinyl Chloride Polymer 1
After mixing 00 parts by weight, 40 parts by weight of di-2-ethylhexyl phthalate, 3 parts by weight of a stabilizer, and a small amount of ultramarine blue,
The number of FEs per 50 cm ^{2 of the} sheet obtained by kneading with a roll at 160 ° C. for 5, 7, and 9 minutes was counted.

Example 1 450 kg of deionized water and a dispersant of the type and amount shown in Table 1 were charged as an aqueous solution or a mixed solution of methyl alcohol and water into a stainless steel polymerization container having an internal volume of 1 cubic meter, and then the system was vacuumed. After nitrogen replacement, 400 kg of vinyl chloride monomer and 0.03 part by weight of butyl neodecanoate as an initiator were charged, and then 8 kg of ethylene was charged with stirring, and the reaction was carried out at a temperature of 55 ° C. up to a conversion rate of 85%. It was The water-soluble cellulose ether had a hydroxypropoxyl group substitution degree of 0.25 and a methoxyl group substitution degree of 1.9, and the viscosity of a 2% by weight aqueous solution at 20 ° C. was 50 cps. Hydroxypropyl methylcellulose (HPMC)
Was used.

After the polymerization, unreacted ethylene and vinyl chloride monomers are recovered, the system is evacuated and replaced with nitrogen, and the ethylene-vinyl chloride copolymer slurry is taken out and dehydrated and dried to obtain a polymer. Part of the analysis was performed according to the method described above, and part of the composition was adjusted according to the method described above and evaluated.

Example 2 A polymer and a composition were obtained in the same manner as in Example 1 except that the amount of PVA (A) used was increased to 0.05 parts by weight.

Examples 3-5 Increase the amount of PVA (C) used to 0.02 parts by weight, or increase the amount of hydroxypropylmethylcellulose (HPMC in Table 1) to 0.05 parts by weight, Alternatively, a polymer and a composition were obtained in the same manner as in Example 2 except that PVA (A) was 0.01 part by weight and PVA (B) was 0.15 part by weight.

Example 6 A polymer and a composition were obtained in the same manner as in Example 2 except that the amount of PVA (C) used was reduced to 0.005 parts by weight.

Example 7 The same procedure as in Example 1 was carried out except that 0.2 part by weight of polyoxyethylene sorbitan monostearate as a surfactant was used as the secondary dispersant instead of PVA (C). A coalescence and composition was obtained.

Comparative Examples 1 to 4 PVA (A) to (B), secondary dispersant (C) or HPM
The same procedure as in Example 1 was performed without using any one of C (D).

Table 1 shows the dispersant formulations of Examples and Comparative Examples.

Table 2 shows the measurement results of the examples and comparative examples.

In Comparative Examples 1 and 4, blocks were formed and polymer particles could not be obtained.

In Comparative Example 2, the composition prepared from the obtained polymer was inferior in thermal stability.

In Comparative Example 3, the obtained polymer was a polymer having inferior plasticizer absorption and fish eye characteristics.

Examples 1 to 7 were polymers and compositions having good thermal stability without various problems as seen in Comparative Examples.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

As described above, according to the present invention, ethylene PVC having excellent thermal stability and less fish eyes can be obtained.

Claims (9)

[Claims] 1. A vinyl chloride and ethylene as essential components,
A mixture with other copolymerizable monomers (hereinafter referred to as a monomer mixture) is suspension-polymerized in an aqueous medium in the presence of an oil-soluble polymerization initiator and a dispersion stabilizer to give an ethylene composition of 0.1 to 25. % Ethylene, vinyl chloride composition 75-99.9% by weight ethylene-
In the method for producing a vinyl chloride copolymer, as the dispersion stabilizer, (A) a partially saponified polyvinyl alcohol having a saponification degree of 70 to 90 mol% and an average degree of polymerization of 1500 to 3000 (hereinafter referred to as PVA), (B)
The degree of saponification is 70 to 90 mol% and the average degree of polymerization is 300 to
1000 PVA, (C) secondary dispersion stabilizer, and (D)
A method for producing an ethylene-vinyl chloride copolymer, which comprises using a water-soluble cellulose ether together. 2. The amount of the dispersion stabilizer (A) used is 0.01 to 0.5 part by weight and the amount of (B) used is 0.05 to 1 with respect to 100 parts by weight of the monomer mixture. The method for producing an ethylene-vinyl chloride copolymer according to claim 1, wherein the amount of (D) used is 0.01 to 0.5 part by weight. 3. The secondary dispersion stabilizer (C) has a saponification degree of 20.
-65 mol% and an average degree of polymerization of 100-1000, which is oil-soluble PVA, and is used in an amount of monomer mixture 10
It is 0.005-0.1 weight part with respect to 0 weight part, The manufacturing method of the ethylene-vinyl chloride copolymer of Claim 1 or 2 characterized by the above-mentioned. 4. A dispersion stabilizer (B) :( C) in a weight ratio of 5:
1 to 20: 1, and the weight ratio of (A) :( B) is 1: 2 to 1:15, and the weight ratio of (A) :( D) is 1: 1 to 5: 1. The method for producing an ethylene-vinyl chloride polymer according to claim 3, wherein the ethylene-vinyl chloride polymer is present. 5. The ethylene-vinyl chloride copolymer according to claim 1 or 2, wherein the secondary dispersion stabilizer (C) is a surfactant having a hydrophilic / hydrophobic balance of 15 or less. Manufacturing method. 6. The use amount of the secondary dispersion stabilizer (C) is 0.05 to 2.0 parts by weight with respect to 100 parts by weight of the monomer mixture. Process for producing ethylene-vinyl chloride copolymer. 7. Hydroxypropyl in which the water-soluble cellulose ether has a degree of hydroxypropoxyl group substitution per glucose unit of 0.15 to 0.25 and a degree of methoxyl group substitution of 1.4 to 1.9. The method for producing an ethylene-vinyl chloride copolymer according to claim 1, which is methyl cellulose. 8. The method for producing an ethylene-vinyl chloride copolymer according to claim 1, wherein a compound having a mercapto group and a hydroxyl group is used as a molecular weight modifier. 9. A method for obtaining a vinyl chloride resin composition by mixing an ethylene-vinyl chloride copolymer and a composite metal soap-based stabilizer, wherein the ethylene-vinyl chloride copolymer is the product of claims 1-8. A vinyl chloride resin composition, which is an ethylene-vinyl chloride copolymer obtained by any one of the methods.