JP2002332308A - Process for producing vinyl chloride based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a vinyl chloride based resin which can add PVA having a thermal stability-improving effect on the vinyl chloride based resin with good efficiency and in any amount in accordance with the level of thermal stability to be required without adversely affecting the polymerization stability and quality characteristics and gives the vinyl chloride based resin having excellent thermal stability and fabricable in a wide range of fabrication conditions in fabricating molded articles by the use of a composite metallic stabilizer. SOLUTION: In producing the vinyl chloride based resin by subjecting a vinyl chloride based monomer to suspension polymerization in an aqueous medium, PVA is added to the resin suspension after the polymerization and/or the hydrated resin after the dehydration of the above resin suspension.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a vinyl chloride resin. More specifically, the present invention relates to a method for producing a vinyl chloride resin having excellent thermal stability when processing a molded article using a composite metal stabilizer such as a calcium-zinc compound and capable of being molded in a wide range of fields and molding conditions.

[0002]

2. Description of the Related Art Vinyl chloride resins are used in a wide range of applications from construction materials such as pipes, corrugated sheets and electric wires to food and medical fields such as food wrapping films and medical blood bags. In the above, a composite metal stabilizer such as calcium-zinc, which is more toxic than lead or tin stabilizers generally used in other applications, is preferably used for safety reasons. Furthermore, in the field of construction materials and civil engineering, the replacement of water and metal pipes and joints with complex metal stabilizers such as calcium-zinc and barium-zinc, which are less toxic and have a lower environmental impact, has been studied. In general, the field of processed products using composite metal stabilizers is expected to expand. However, composite metal stabilizers are generally inferior in thermal stability to lead and tin-based stabilizers, and it is known that a rapid blackening phenomenon (zinc burning) occurs particularly with composite metal stabilizers using zinc. In order to be used in a wide range of fields and a wide range of molding processing conditions in place of a lead or tin-based stabilizer, further improvement in thermal stability is desired. In order to improve such disadvantages, it has been known that composite metal stabilizers improve heat stability in combination with polyols, phosphites, epoxy compounds, and the like. It is called a stabilizing aid. By the way, in a method of producing a vinyl chloride resin by a suspension polymerization method, PVA generally used as a dispersant belongs to the above-mentioned polyols and has a stabilizing aid effect. Several patents have been reported to improve the thermal stability of vinyl chloride resins.
For example, a method of polymerizing in the presence of PVA (Japanese Unexamined Patent Publication No.
117545), a method of polymerizing in the presence of PVA and an epoxy compound (JP-A-49-104939),
A method in which polymerization is carried out in the presence of A and a water-soluble cellulose ether (Japanese Patent Laid-Open No. 6-212909) is disclosed.

[0003] However, PVA is originally used as a dispersant for suspension polymerization, and its type and amount greatly affect the quality and shape of the obtained vinyl chloride resin. If a large amount of PVA is added to the polymerization, the suspension state in the polymerization machine will be overdispersed, the size of the suspended oil droplets will decrease, and the resulting resin fine powder will increase, or conversely, abnormally large particles In addition to obtaining a resin having a non-uniform particle size distribution due to non-uniform mixing of (coarse particles), in the worst case, polymerization stability is greatly impaired and abnormal polymerization occurs. In particular, highly saponified PV of 90% or more, which has a high thermal stability improving effect.
A and completely saponified PVA are hardly adsorbed on the vinyl chloride monomer, which is the main component of the oil droplets, and greatly reduce the polymerization stability, so that it is generally difficult to add them to the polymerization system. Further, a resin having a non-uniform particle size distribution or a resin containing a large amount of fine powder is not preferable in terms of quality because the processability and powder fluidity are greatly impaired even if abnormal polymerization is not caused.

[0004]

That is, an object of the present invention is to provide a PVA having a thermal stability improving effect efficiently and at the required thermal stability level without impairing polymerization stability and quality characteristics. Any amount can be added to the vinyl chloride resin, and when processing molded products using composite metal stabilizers such as calcium-zinc and barium-zinc, it has excellent thermal stability and can be used in a wide range of molding conditions. An object of the present invention is to provide a method for producing a moldable vinyl chloride resin.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above problems, and as a result, it has been found that PVA is not a polymerization system but a resin suspension after polymerization and / or a resin suspension dehydration. The desired vinyl chloride-based resin, which can be added to the subsequent dehydrated resin as an aqueous solution without impairing polymerization stability and quality characteristics, and in which the amount of PVA can be arbitrarily changed according to the required thermal stability level The present inventors have found a production method of the present invention, and have completed the present invention. That is, the present invention provides (1) suspension polymerization of a vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer in an aqueous medium to obtain a vinyl chloride resin. In the production, a method for producing a vinyl chloride-based resin is characterized in that PVA is added to a resin suspension after polymerization and / or a dehydrated resin after dehydration of the resin suspension. PVA has a saponification degree of 50 to 1
The method for producing a vinyl chloride resin according to claim 1, wherein the PVA is 00 mol% of PVA (claim 2),
(3) PVA is used in an amount of 0.0001 to 5 parts by weight per 100 parts by weight of dehydrated resin after dehydration of resin suspension and / or resin suspension.
3. The method for producing a vinyl chloride resin according to claim 1 or 2, wherein the addition is carried out so as to be in parts by weight, and (4) adding PVA as an aqueous solution. A method for producing a vinyl chloride resin according to claim 1, 2 or 3 (claim 4).

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As the PVA used in the present invention, PVA having a saponification degree of 50 to 100% is preferably used. Since the higher the degree of saponification, the higher the effect of improving the thermal stability, PVA having a degree of saponification of 75 to 100% is particularly preferable. PVA having a degree of saponification of less than 50% has a low effect of improving the thermal stability, and thus needs to be added in a large amount. The average degree of polymerization of PVA is not particularly limited because it does not affect the effect of improving the thermal stability.
A is preferable because it can be easily handled in an aqueous solution. PVA
Is 100 parts resin (equivalent to dry resin) relative to the resin suspension and / or the dehydrated resin after dehydration of the resin suspension.
It is preferred to add in the range of 0.001 to 5 parts by weight based on parts by weight. If the amount is less than 0.001 part by weight, the effect of improving the thermal stability is small, and if it is more than 5 parts by weight, the properties as a vinyl chloride resin may be affected. It is particularly preferable to add in the range of 0.01 to 1 part by weight even within the above addition range. Further, two or more different PVAs may be used in combination, but it is preferable to use the total addition number within the above range.

[0007] When PVA is added in the form of solids such as crystals, it is difficult to uniformly disperse it in the resin, and the solids may remain as fish eyes or foreign substances during processing. Therefore, it is desirable to add PVA as a solution. In particular, it is preferable to add as an aqueous solution. 0.1-20% by weight of PVA aqueous solution to be added
Are preferred. At a high concentration of 20% by weight or more, the viscosity of the aqueous solution increases, and it becomes difficult to uniformly disperse the solution when added to the resin. Conversely, if the concentration is as low as 0.1% by weight or less, the efficiency of addition may decrease, or the moisture content may increase and the drying efficiency may decrease. Even within the above range, it is particularly preferable to set the concentration in the range of 1 to 10% by weight.

[0008] PVA can be added to the resin suspension after polymerization and / or the dehydrated resin after dehydration of the resin suspension. The addition to the resin suspension is simple and has the merit of uniform dispersion, but it is difficult to selectively adsorb to the vinyl chloride resin because part of PVA migrates into water, and the addition efficiency is poor, The method of adding to the cake-like dewatered resin after dehydration of the resin suspension is more preferable.

The dehydrated resin referred to herein is obtained by dehydrating a resin suspension obtained by polymerization with a dehydrator, and the water content is not particularly limited, but is usually about 10 to 20% by weight. Resin containing water.

The vinyl chloride resin in the present invention includes, for example, a vinyl chloride homopolymer resin and a vinyl chloride copolymer resin. As a monomer copolymerizable with a vinyl chloride monomer for producing a vinyl chloride copolymer resin,
For example, alkyl vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether,
Α-olefins such as ethylene and propylene; alkyl (meth) acrylates such as methyl acrylate and methyl methacrylate; and vinylidene compounds such as vinylidene chloride.

According to the present invention, the vinyl chloride resin to which PVA can be added can be obtained by a known suspension polymerization method, and is not limited by the suspension polymerization method.

The vinyl chloride resin obtained as above is mixed with a composite metal stabilizer, and is molded.
Shows excellent thermal stability and moldability.

The term "composite metal stabilizer" as used herein refers to a stabilizer used in combination (combination) in order to obtain a synergistic effect of a plurality of stabilizers. Particularly, zinc, an alkali metal and / or an alkaline earth metal are used. And the like, and are preferably used. This composite metal stabilizer is a non-toxic, long-lasting heat which is a weak point of zinc by combining it with an alkali metal and / or alkaline earth metal while taking advantage of the characteristics of zinc which is non-toxic and has excellent initial coloring properties and hydrogen chloride capturing ability. It is an excellent stabilizer that can also improve the stability and can be expected to produce a synergistic effect by the combination. Examples of metals to be combined include lithium, sodium, potassium, magnesium, calcium, barium and the like. Among them, a combination of calcium and zinc or a combination of barium and zinc is preferable. Zinc and associated metals are commonly used as organic acid salts such as, but not limited to, caprylic acid, lauric acid, palmitic acid, stearic acid, and the like. Moreover, it is also possible to combine the above-mentioned stabilizers such as polyols, phosphites and epoxy compounds.

[0014]

EXAMPLES Specific examples of the present invention will be described below in detail, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 PVA having an average polymerization degree of 2000 and a saponification degree of 80 mol% (hereinafter abbreviated as PVA-1) was used as a dispersion stabilizer in a stainless steel polymerization machine equipped with a stirrer and jacket having an internal volume of 1500 liters. ) In an amount of 0.05 parts by weight (based on 100 parts by weight of vinyl chloride monomer) in terms of PVA weight, and 0% of tert-butyl peroxy neodecanoate as an oil-soluble initiator. .015 parts by weight (the same) and 3,5,5-trimethylhexanoyl peroxide (0.02 parts by weight) were charged, and the pressure was reduced by a vacuum pump to remove oxygen. Subsequently, 500 kg of a vinyl chloride monomer was charged, and 120 parts by weight of deionized water heated to 60 ° C. (the same) was further charged. The temperature of the system was raised to 64 ° C. to start polymerization, and subsequently polymerization was carried out at a constant temperature. When the polymerization addition rate reaches 75%,
Unreacted vinyl chloride monomer was collected out of the system to terminate the reaction. After removing the vinyl chloride monomer in the polymerization machine to the atmospheric pressure, the vinyl chloride resin suspension in the polymerization machine is discharged to a mixing tank, and sequentially dehydrated by a dehydrator using centrifugal separation to obtain a dehydrated resin having a water content of 15%. I got The same 3% by weight aqueous solution of PVA-1 as used in the polymerization was used for the dehydrated resin.
With respect to 0 parts by weight, 0.05 parts by weight in terms of PVA was added and uniformly mixed in the same dehydrated resin. The mixture was dried in a fluidized drier to obtain a vinyl chloride resin. Next, the average particle size and particle size distribution of the obtained resin, and calcium-
The thermal stability of the zinc blend was evaluated. First, the average particle size and the particle size distribution were measured in accordance with JIS K-6721.
Using a sieve of 2, 60, 80, 100, 120, 145, 200 mesh, sieving with a sieve shaker,
% Was defined as the average particle diameter (μm). The particle size distribution was measured by measuring the weight of the vinyl chloride resin remaining on each mesh, and expressed as a weight percentage. Of these, the amount remaining in the 42 mesh was defined as coarse particles (coarse particle ratio), and the amount passing through 200 mesh was defined as fine powder (fine powder ratio). Table 2 shows the results. Next, the thermal stability of the calcium-zinc blend was determined by blending at the formulation shown in Table 1 below, and at a temperature of 170.
C., kneading for 3 minutes using a roll having a rotation speed of 20 rpm,
A roll sheet having a thickness of 0.7 mm was prepared, the roll sheet was left in an oven at a temperature of 160 ° C., the roll sheet was observed every 10 minutes, and the blackening time of the roll sheet was measured. The results are shown in Table 2.

[0016]

[Table 1] (Example 2) 3% by weight of PVA-1 added to dehydrated resin
Except that the amount of the aqueous solution was doubled from 0.05 part by weight to 0.1 part by weight in terms of PVA with respect to 100 parts by weight of the dehydrated resin.
This was performed in the same manner as in Example 1 above. Table 2 shows the results.

Example 3 A partially saponified polyvinyl alcohol having an average degree of polymerization of 2600 and a saponification degree of 96% (hereinafter abbreviated as PVA-2) was used instead of a 3% by weight aqueous solution of PVA-1.
Of a 3% by weight aqueous solution of
The same procedure as in Example 1 was performed except that 0.1 part by weight in terms of A weight was added. Table 2 shows the results.

Example 4 Instead of adding a 3% by weight aqueous solution of PVA-1 to a dehydrated resin, a 3% by weight aqueous solution of PVA-1 was added to the resin suspension after polymerization. The same procedure as in Example 1 was performed except that 0.1 parts by weight of PVA was added to the parts by weight. Table 2 shows the results.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1, and a 3% by weight aqueous solution of PVA-1 was not added to the dehydrated resin. The subsequent treatment and evaluation were carried out in the same manner as in Example 1.
Table 2 shows the results.

Comparative Example 2 In the polymerization of Example 1, the amount of a 3% by weight aqueous solution of PVA-1 added before the polymerization was adjusted to 0.0
Polymerization was carried out by doubling from 5 parts by weight to 0.1 parts by weight, and a 3% by weight aqueous solution of PVA-1 was not added to the dehydrated resin. The subsequent treatment and evaluation were performed in the same manner as in Example 1. Table 2 shows the results.

Comparative Example 3 In addition to 0.05 parts by weight of a 3% by weight aqueous solution of PVA-1 added before polymerization in the polymerization of Example 1, 0.1 part by weight of a 3% by weight aqueous solution of PVA-2 was further added. Was added to carry out polymerization. Table 2 shows the results.

[0022]

[Table 2] (Results of Evaluation) From the results shown in Table 2, the following points can be observed.

(1) In all of Examples 1 to 4 in which PVA was added to a dehydrated resin or a resin suspension, the blackening time was longer than that in Comparative Example 1 in which PVA was not added after polymerization, and the PVA was thermally stable. It can be seen that there is an improvement effect. In addition, the effect of improving the thermal stability in the addition method is higher as the degree of saponification of the PVA to be added is higher and as the number of added parts is larger.

(2) In Comparative Example 2 in which the number of PVA added at the time of polymerization was doubled, the blackening time was longer than that in Comparative Example 1, and even when added to the polymerization system, the effect of improving the thermal stability could be obtained. As can be seen, it can be seen that the average particle size is greatly reduced as compared with Comparative Example 1, and both the fine powder ratio and the coarse particle ratio are increased and the particle size distribution is non-uniform.

(3) In Comparative Example 3 in which highly saponified PVA was used during the polymerization, abnormal polymerization occurred, and the highly saponified PVA was added to the polymerization system.
It turns out that it is difficult to add VA.

[0026]

According to the present invention, PVA having an effect of improving thermal stability can be efficiently converted into an arbitrary amount in accordance with a required thermal stability level without impairing polymerization stability and quality characteristics. A vinyl chloride resin that can be added to vinyl resins and has excellent thermal stability and can be molded under a wide range of molding processing conditions when processing molded articles using composite metal stabilizers such as calcium-zinc and barium-zinc. A resin can be obtained.

Claims (4)

[Claims] When a vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium to produce a vinyl chloride resin, A polyvinyl chloride resin characterized by adding partially saponified and / or completely saponified polyvinyl alcohol (hereinafter referred to as PVA) to a resin suspension after polymerization and / or a dehydrated resin after dehydration of the resin suspension. Production method. 2. PVA having a saponification degree of 50 to 100 mol%.
The method for producing a vinyl chloride resin according to claim 1, wherein the resin is VA. 3. The method according to claim 1, wherein PVA is added in an amount of 0.0001 to 5 parts by weight per 100 parts by weight (in terms of dry resin) of the resin suspension and / or dehydrated resin after dehydration of the resin suspension. Or the method for producing a vinyl chloride resin according to 2. 4. The method for producing a vinyl chloride resin according to claim 1, wherein the PVA is added in the form of an aqueous solution.