JPS5996152A - Production of polyvinyl chloride composition - Google Patents

Abstract

PURPOSE:To obtain a polyvinyl chloride compsn. having improved moldability, by carrying out the polymn. of vinyl chloride monomer or a mixture thereof with other monomer in the presence of a polymn. initiator in several stages so as to obtain a specified relationship with regard to the degree of polymn. CONSTITUTION:The polymn. of vinyl chloride monomer or a mixture thereof with other copolymerizable monomer in the presence of a polymn. initiator is carried out in several stages in such a manner that the polymn. of the remaining vinyl chloride monomer or mixture in the second and subsequent polymn. stages is carried out in the presence of the vinyl chloride polymer obtd. by the foregoing polymn. stage under such conditions that the resulting polymer has a weight- average degree of polymn. smaller than that of the polymer obtd. by the first polymn. stage and that the following relationship can hold: Pomega>1,000, Q>2.8 and 65wt%<=omega], <=90wt%, where Pomega is weight-average degree of polymn. of polyvinyl chloride compsn., Q is MW distribution of polyvinyl chloride compsn. and omega1 is the proportion of vinyl chloride polymer obtd. by the first polymn. stage in the total polyvinyl chloride compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polyvinyl chloride composition (hereinafter also referred to as single KPVC). More specifically, the present invention relates to a method for producing PVC with significantly improved moldability.

"Number average degree of polymerization" of PVC in the present invention.

"Weight average degree of polymerization JtrZ+x average degree of polymerization" and "molecular weight distribution" are defined by the following formula.

ni Σn1Pi'' Molecular weight distribution Q = Po/Pn where Pi is the degree of polymerization of the i-th polymer constituting PVC, and ni is the number of molecules of the i-th polymer.

In the present invention, the term vinyl chloride polymer, polyvinyl chloride, polyvinyl chloride composition or PVC refers to a homopolymer of vinyl chloride and a mixture of vinyl chloride monomer and other monomers copolymerizable. It is used as a general term for vinyl chloride copolymers obtained by

Polyvinyl chloride is widely used as a versatile resin because it is inexpensive compared to other resins, and the various molded products obtained from it have excellent physical properties.
Its moldability and mechanical strength are not fully satisfactory. In particular, the moldability of polyvinyl chloride is significantly inferior to that of other general-purpose resins.

Generally, polyvinyl chloride has a weight average degree of polymerization of 600 to 15.
00 resin is often used. Polyvinyl chloride has the advantage that as the weight average degree of polymerization increases, the rigidity, toughness, and heat resistance of the molded article increase, but on the other hand, it has the disadvantage that molding processability such as gelability and melt flowability is significantly inferior. When the weight average degree of polymerization of polyvinyl chloride exceeds 1000, the above properties are particularly pronounced, and although it has excellent mechanical strength and thermal stability, it has poor moldability (because it is not used satisfactorily). .

A method of broadening the molecular weight distribution has been reported as a means of improving the moldability of polyvinyl chloride. For example, B,
P, -1,279,502, the polyvinyl chloride obtained by polymerizing in the first stage at a low temperature and then in the second stage at a higher temperature than the first stage has a molecular weight distribution similar to that of conventional polychloride. It is stated that it spreads more than vinyl. The polyvinyl chloride obtained in this way has excellent processability and is characterized in that the mechanical strength of the molded product is maintained well. However, the polyvinyl chloride obtained by this invention has an M-view composition of polyvinyl chloride with a high degree of polymerization obtained in the first stage polymerization.
5% by weight, PQ)/Pn (molecular weight distribution expressed as the ratio of weight average degree of polymerization to number average degree of polymerization) is 3.2 or less, and PZ+1/Po (Z +1 average degree of polymerization and weight The average degree of polymerization (molecular weight distribution expressed as a ratio) is 5
．． It is polyvinyl chloride having a characteristic value of 0 or more.

Also, U, S, P, -3,956,251 have B, P,
-1, 279,502 invention, i.e. first stage polymerization is carried out at a polymerization temperature in the range of 35°C to 55°C, and then the polymerization is completed at a polymerization temperature in the range of 60°C to 80°C. It is stated that polyvinyl chloride with good processing fluidity can be obtained by adopting the method of However, in this case, the weight average degree of polymerization of the polyvinyl chloride finally obtained is 1000 or less.

However, even if these methods are adopted, for polyvinyl chloride with a weight average degree of polymerization exceeding 1000, not only cannot the effect of improving processing properties be expected, but also there is a drawback that mechanical strength, thermal stability, etc. are reduced. It became clear that

The present inventors have maintained the advantages of the excellent mechanical strength and thermal stability of polyvinyl chloride, which has a weight average degree of polymerization of over 1000, while improving its moldability, which is said to be a drawback. As a result of repeated research into a method for obtaining polyvinyl chloride with excellent moldability that can be applied in the field of molding processing, the present invention has been completed.

That is, in the present invention, vinyl chloride monomer or a mixture of vinyl chloride monomer and other copolymerizable monomers is polymerized in multiple times in the presence of a polymerization initiator, and each time the polymerization In the method for producing a polyvinyl chloride composition consisting of a vinyl chloride polymer obtained in the second and subsequent polymerizations, the polymer obtained in the first polymerization is The remaining vinyl chloride monomer or a mixture thereof is polymerized so that the weight average degree of polymerization is smaller than that of the vinyl chloride polymer obtained, and the weight average degree of polymerization of the polyvinyl chloride composition is determined as PL, 1, molecular weight distribution. When Q is the proportion of the vinyl chloride polymer obtained in the first polymerization in the polyvinyl chloride composition, P(, > 1000, Q > 2.8, and 65% by weight ≦ ω) , ≦90% by weight.

In the present invention, other monomers that can be copolymerized with the vinyl chloride monomer used are not particularly limited, and known monomers can be used. In general, those having ethylenically unsaturated groups, such as olefin compounds such as ethylene and propylene; vinyl esters such as vinyl acetate and vinyl propionate; unsaturated monocarboxylic acids such as acrylic acid and α-alkyl acrylic acid; Alkyl esters, amides, namely acrylic acid, methacrylic acid, ethyl acrylate, methyl methacrylate, acrylic acid amide, methacrylic acid amide: unsaturated nitriles such as acrylonitrile; maleic acid! Unsaturated dicarboxylic acids such as fumaric acid, alkyl esters thereof, and anhydrides thereof; vinyl alkyl ethers such as vinyl methyl ether and vinyl ethyl ether; and various other known copolymerizable monomers are preferably used. Ru.

In the present invention, the polymerization of vinyl chloride monomer or a mixture of vinyl chloride monomer and other copolymerizable monomer is carried out in multiple steps.

Usually, the polymerization is carried out in two parts, but polymerization can be carried out in three or more parts. , the remaining vinyl chloride monomer or a mixture of the vinyl chloride monomer and other copolymerizable monomers is polymerized.

In this case, the 5&C vinyl chloride polymer must be polymerized so that the weight average degree of polymerization is lower than that of the vinyl chloride polymer obtained in the first polymerization.

In this way, a vinyl chloride polymer is obtained in each polymerization, and finally a polyvinyl chloride composition (PVC) made of the above-mentioned vinyl chloride polymer is obtained.

If polyvinyl chloride with a high degree of polymerization and polyvinyl chloride with a low degree of polymerization are simply mixed together without following the polymerization method described above, even if the conditions such as the degree of polymerization 2 molecular weight distribution of the present invention described later are Even if the above conditions are met, the resulting product will have spots, which is not preferable.

In the present invention, the molecular weight distribution of PVC obtained by the above polymerization method must be 2.8 or more. Preferably,
It is 3.5 or more. The molecular weight distribution of PVC varies depending on the polymerization conditions, but is generally in the range of 2.0 to 2.5. The molecular weight distribution of PVC with a weight average degree of polymerization of less than 1000 is generally in the range of 2.0 to 2.2, and when the molecular weight distribution is increased to 2.5 or more, the fluidity is significantly improved, but when the weight average degree of polymerization is less than 1000, It has been found that for PVC exceeding 2.5%, the improvement in moldability is small even if the molecular weight distribution is widened to about 2.5. The present inventors have determined that the weight average degree of polymerization is 1
As a result of systematic investigation of the molecular weight distribution and molding processability of PvC exceeding 000, it was found that controlling the molecular weight distribution to 2.8 or higher, preferably 3.5 or higher, significantly increases processing fluidity.

Therefore, in the case of PVC having a weight average degree of polymerization exceeding 100, it is necessary to set the molecular weight distribution to 2.8 or more.

In order to obtain PVC with a weight average degree of polymerization exceeding 1000 and a molecular weight distribution of 2.8 or more,
The following conditions are appropriate. In the present invention, P is the weight average degree of polymerization of the vinyl chloride polymer with a high degree of polymerization obtained in the first polymerization. )1. The weight average degree of polymerization of the vinyl chloride polymer with a low degree of polymerization obtained in the second and subsequent polymerizations is P (1)
2, the ratio P(I)l/P,' is 3.
It is preferable that it is 4 or more. In other words, p 6) 1
When /p, 2 is smaller than 3.4 and the degree of polymerization of the finally obtained PvC exceeds 1000, the molecular weight distribution is unlikely to be 2.8 or more.

In the present invention, even if the weight average degree of polymerization of PVC exceeds 1000 and the molecular weight distribution is 2.8 or more, the degree of polymerization is 1
The mechanical strength and thermal stability that are characteristics of PvC over 000 cannot necessarily be maintained. In the present invention, it is necessary to satisfy the condition that the amount of vinyl chloride polymer obtained in the first polymerization among multiple polymerizations is within a certain range. That is, when ωl is the proportion of the vinyl chloride polymer obtained in the first polymerization in PVC, the first polymerization must be performed such that 65% by weight≦ωl 590% by weight. If ω is less than 65% by weight, the amount of vinyl chloride polymer with a low degree of polymerization in the final PVC will be large (which is unfavorable from the viewpoint of mechanical properties and thermal stability. On the other hand, ωl exceeds 90% by weight, in order to widen the molecular weight distribution to 2.8 or more, preferably 3.5 or more,
It is necessary to significantly reduce the difference in the weight average degree of polymerization between the vinyl chloride polymer of the first polymerization and the vinyl chloride polymer of the second and subsequent polymerizations, resulting in the disadvantage that the physical properties of the molded product are impaired. Undesirable.

When PVC has a weight average degree of polymerization of more than 1000 and has a wide molecular weight distribution, preferably 2.8 or more, preferably 3.5 or more,
The moldability is also correlated to some extent with the particle structure. 3
If it is mixed in the form of secondary particles, not only will the flow processability be insufficiently improved, but the surface properties of the soft molded product will be poor (
It may happen. Therefore, it is necessary to mix at least the order of secondary particles, and so that the vinyl chloride polymer with a low degree of polymerization exhibits a kind of plasticity, it is necessary to mix the tertiary particles of the vinyl chloride polymer with a high degree of polymerization. Preferably, it is distributed within the particles. Therefore, in the first polymerization, a vinyl chloride polymer with a high degree of polymerization is polymerized to form an agglomerated structure of porous secondary particles, and then a vinyl chloride polymer with a low degree of polymerization is polymerized to obtain a high degree of polymerization. It is desirable that the gaps between the secondary particles of the vinyl chloride polymer be filled with an order of less than the secondary particles of the vinyl chloride polymer having a low degree of polymerization.

In the present invention, the conditions for the first polymerization are not particularly limited and may be selected from known polymerization conditions. for example,
Add the necessary dispersant and initiator in an aqueous medium,
By polymerizing the monomers at a polymerization temperature in the range of 0°C to 55°C, P with a weight average degree of polymerization of more than 1000 can be obtained.
You can get VC. Similarly, the second and subsequent polymerizations are not particularly limited and can be appropriately adopted from known polymerization conditions. 60
By raising the temperature to a temperature in the range of 80°C to 80°C and further continuing the polymerization at that temperature, the vinyl chloride polymer obtained in the second and subsequent polymerizations was obtained in the first polymerization. It is possible to make the degree of polymerization smaller than that of vinyl chloride polymer.

In the present invention, when obtaining a vinyl chloride polymer with a high degree of polymerization in the first polymerization, a crosslinking agent may be used. Furthermore, when a vinyl chloride polymer having a low degree of polymerization is polymerized in the second and subsequent polymerizations, a chain transfer agent can be suitably used.

Although any known crosslinking agent may be selected and used, polyfunctional crosslinking agents are generally used. Examples of polyfunctional crosslinking agents include acrylic acid or methacrylic acid of monokpolyalkylene glycols such as ethylene glycol diacrylate, diethylene glycol di7 acrylate, 1,3-bupylene glycol dimethacrylate, and 1,4-butanediol dimethacrylate. Esters; di- or tri-7lyl compounds such as divinylbenzene, di7lyl-7thaleate, diallyl maleate, diallyl succinate, triallyl-7dine; and 7-lyl compounds such as 7lyl methacrylate and allyl acrylate. Crosslinking agents affect the processability of PvC and the mechanical properties and finished state of the product, so care must be taken when using them. That is, by using a crosslinking agent, it is possible to easily obtain a vinyl chloride polymer with a high degree of polymerization in the first polymerization, and
The presence of a crosslinked vinyl chloride polymer is preferable because it works to improve mechanical strength, but if a large amount of crosslinking agent is used, the melt viscosity during processing will increase, resulting in a decrease in moldability, and at the same time, the product This may cause pops to occur. Therefore, the amount of crosslinking agent to be used is not necessarily limited as it varies depending on the polymerization temperature, type, etc., but in general, the amount of crosslinking agent used is from 0 to 5% by weight preferably 0.01-1
Preferably, it is in the range of % by weight.

Similarly, the chain hyperactivity agent may be appropriately selected from known ones and used, but generally, for example, chlorinated hydrocarbons such as carbon tetrachloride and trichlorethylene; and propionaldehyde.

Aldehydes such as butyraldehyde; organic mercaptans such as dodecyl mercaptan and 2-mercaptoethanol are preferably used. The amount of chain transfer agent used varies depending on the polymerization temperature, type, etc., so it is not necessarily limited, but in general, it is used to , θ~10.
The amount of ia should preferably be in the range of 0.01 to 5M %.

In the polymerization of monomers in the present invention, polymerization initiators that are generally used include, for example, lauroyl peroxide,
Tertiary glycyl peroxide xybibalate, benzoyl peroxide, impulpyl dioxycarbonate.

7zobisisobutyronitrile, α, α1-7zobis-4
-Methoxy-2,4'-dimethylvaleronitrile and other known oil-soluble polymerization initiators are preferably used. Preferably, the polymerization is carried out in the presence of at least two types of polymerization initiators appropriately selected from among these polymerization initiators. In that case, all polymerization initiators are generally added to the polymerization system during the first polymerization, but it is preferable to use low-temperature active ones during the first polymerization and high-temperature active ones during the second and subsequent polymerizations. A sequential addition method is adopted in which the sample is added at the same time. Further, the amount of the polymerization initiator to be used may be selected from a range such that the total amount is 0.01 to 5% by weight based on the monomers used.

The method of the present invention is suitably employed in suspension polymerization of vinyl chloride monomer or a mixture of vinyl chloride monomer and other copolymerizable monomers, but the polymerization method is not particularly limited. It is also applicable to polymerization methods selected from known bulk polymerization methods, emulsion polymerization methods, and gas phase polymerization methods. In addition, in carrying out the present invention, the polymerization temperature, polymerization pressure, polymerization time, etc. may be determined according to the conditions conventionally adopted when polymerizing vinyl chloride monomers (although these are not particularly limited). It's not a thing.

As mentioned above, the Pvc obtained by implementing the present invention is
P with a high degree of polymerization with a weight average degree of polymerization exceeding 1000
Although it is a vC, it is a resin that has significantly improved moldability compared to conventional PVC. The reason for this is that in the case of PVC with a weight average degree of polymerization exceeding 10oO, if the molecular weight distribution is controlled to 2.8 or more, it is possible to reach the true molten state of PvC during molding.
The particle structure is similar to a kind of two-phase structure in which the gaps between secondary particles of high polymerization degree vinyl chloride polymer are filled with low polymerization degree vinyl chloride polymer on an order of magnitude smaller than that of the secondary particles. Conceivable. It is presumed that these two effects act as a mutual effect, resulting in extremely excellent moldability. As a result, the weight average degree of polymerization, which was previously impossible to mold, has been reduced to 1OO without sacrificing its excellent physical properties.
The characteristic that hard and soft molding of PVC exceeding 0.0 is significantly facilitated is obtained.

EXAMPLES In order to explain the present invention in more detail, Examples and Comparative Examples will be described below, but the present invention is not limited to these Examples. In addition, the measured values shown in Examples and Comparative Examples were based on the following measurement method.

(1) Weight average degree of polymerization The specific viscosity was measured according to JISK-6721 and calculated as Mfi average degree of polymerization.

(2) Molecular weight distribution P
It was calculated as (t)/Pn. In detail, a sample of 0.1% by weight of PvC dissolved in tetrahydrofuran was
The molecular weight distribution curve was obtained through a column consisting of polystyrene glue with molecular weight fractionation in the range of 10'' to 5X107, and then the calibration curve was used to calculate the molecular weight distribution P (, l/P
n was calculated. The PVC calibration curve used was a calibration curve created using a polystyrene standard sample that was corrected based on the universal calibration method.

(3) Melt viscosity Melt fluidity was measured and melt viscosity values were calculated using the Koka type flow tester method, which is employed when investigating the flow characteristics of PvC. In detail, PvC containing hard tin is 1
The roll-formed sheet having a thickness of about 1 mm obtained by cross-poling at 60"C was used as a sample for measurement.

The PVC-+7 pull to 60? 10 at 160℃ under load
After preheating for minutes, under a heating rate of 3°C/min, a load of 9 was applied to 150 to measure the shear rate at each temperature.
The melt viscosity value was determined using the following formula.

(4) Gelation time The gelation time was measured according to a measurement method using a Zlavender Plus Tucoder, which is commonly used when investigating the molding processability of PVC.

(5) Tensile test After preheating the formed sheet at 180°C for 10 minutes and pressing it at 4oKy/d for 10 minutes, a 1 m thick sheet was punched out into a No. 2 test piece, according to the method of JIS K-7113. Measurements were made at a temperature of 23° C. and a tensile speed of 10 m+/i.

(6) Thermal stability test The blackening time was measured as follows.

A mixed sample prepared by the lead hard compounding method (Example 1, the formulation shown in Table 8) K was kneaded at 175° C. for 5 minutes using a mixing rule to form a sheet of one thickness. Next, this sheet was subjected to a heat deterioration test at iso° C. while the gear was open, and the blackening time was measured.

Example 1 In a 30-ton autoclave equipped with a stirrer, 8 g of partially decomposed polyvinyl alcohol and 3 g of methyl cellulose were dissolved in 12 Kfi of ion-exchanged water! 6 g of inbutisilver oxide was charged as a polymerization initiator, and after degassing the autoclave, vinyl chloride monomer Bx2 was charged and polymerized at the predetermined temperature and for the predetermined time described in the first polymerization conditions in Table 1. Next, 4 g of tertiary-butylperoxypivalate and 2-mercaptoethanol shown in Table 2 as a polymerization initiator were charged into the polymerization system, and the temperature was raised to a predetermined temperature in about io minutes, and the temperature was raised to the specified temperature shown in Table 1. Polymerization was carried out under the second polymerization conditions. The obtained PVC was dried under reduced pressure at 40°C all day and night. The melt viscosity, gelation time and tensile strength of the PvC thus obtained were measured. These results are shown in Table 1. In addition, the above melt viscosity is a measured value at 180 ° C.
The gelation time is the result measured at 165° C. for the mixtures according to the tin hard compounding method shown in Table A. The tensile strength was determined by kneading a mixed sample according to the hard lead compounding method shown in Table 3 at 180°C for 5 minutes using a mixing roll, and then testing this J-ru molded sheet based on the above-mentioned tensile test method. The results are shown in Table 1.The first front seats 11 to 3I are shown as comparative examples.

Table A Table B Among them, Comparative Example 1631 shows the results of PVC subjected to only the first polymerization.

Example 2 In an autoclave number 301 equipped with a stirrer, 6 g of imbutyryl peroxide was charged as a polymerization initiator to 12 kg of ion-exchanged water in which partially saponified polyvinyl alcohol 8I and 3 g of methyl celtose were dissolved, and after degassing the autoclave, vinyl chloride was dissolved. After charging monomer 8KP,
The predetermined temperature described in the second polymerization conditions.

Polymerization was carried out for a predetermined period of time. Next, the polymerization initiator tertiary butyl baroxyvivalate 41! and 2 shown in Table 2.
- Mercaptoethanol is added to the polymerization system for about 10 min.
The temperature was raised to a predetermined polymerization temperature within minutes, and polymerization was carried out under the second polymerization conditions listed in Table 2. The obtained PVC was dried under reduced pressure at 40°C all day and night. The melt viscosity, gelation time, tensile strength, and blackening time of the PVC thus obtained were measured in the same manner as in Example 1. The results are shown in Table 2.

In addition, it is shown in Table 2 1641-91 as a comparative example.

Among them, Comparative Example 1681 is the result of PvC in which the first polymerization was performed. In Comparative Example A9', the first salt and vinyl chloride polymer with a high degree of polymerization obtained based on Example A5' and the second vinyl chloride polymer with a low degree of polymerization were separately polymerized. This is the result of PvC obtained by blending the PVC thus obtained.

Example 3: A 2-ton stainless steel autoclave with a stirrer; ion-exchanged water IKP in which 1.6 g of partially saponified polyvinyl alcohol and 0.7 g of methyl cellulose were dissolved; After charging 0.4 g of inbutylene peroxide, the autoclave was degassed and 350 g of vinyl chloride monomer was charged.
Polymerization was carried out at 47°C for 5 hours. Next, 0.3 g of tertiary glutyl peroxybivalate as an initiator was added to the polymerization system, and the temperature was raised to 78 DEG C., followed by polymerization for 1.2 hours.

The degree of polymerization of the obtained PVC was 2,300. The molecular weight distribution is 5
．． 0 and Pωl /pω”=8.2.ω□=67wt%
It became. The physical properties of the thus obtained PVC were measured in the same manner as in Example 1, and the melt viscosity was 3.6 x 10' voids, and the gelation time was 15.7 minutes.

Example 4 1.5 g of partially saponified polyvinyl alcohol and 0 methyl cellulose were placed in a 2-ton stainless steel autoclave equipped with a stirrer.
．． After charging ion-exchanged water IKp in which 6 p was dissolved, 0.4 g of industyryl peroxide, and 10 g of vinyl acetate, the autoclave was degassed, and then the ionized vinyl monomer 35
0I was charged, polymerized at 40°C for 4.7 hours, and then the initiator tertiary butyl baroxybeverley) 0.1
．． 9 and 4 g of dodecyl mercaptan as a chain transfer agent were added, the temperature was raised to 70° C., and polymerization was carried out for 1 hour. Obtained P
The weight average degree of polymerization, molecular weight distribution and vinyl acetate content of VC were 1580, 3.8 and 2.9% by weight, respectively. Note that this PvC is P,1/P(,,=4.85.
ω,=72% by weight. The physical properties of the PvC thus obtained were measured in the same manner as in Example 1, and the melt viscosity was 2.0×10' poise and the gluing time was 8.3 minutes.

Example 5 A glass autoclave equipped with a stirrer was charged with 100 m of n-pentane, 100 mJ of vinyl chloride monomer, and 0.59 g of imbutyryl peroxide and 0.5 g of lauroyl peroxide as initiators, and the mixture was stirred and polymerized at 37°C for 5 hours. A PvC sheet was obtained. Next, the polymerization temperature was raised to 75°C, gaseous vinyl chloride monomer was continuously pressurized at a pressure of 7.25 KP/cd, and the autoclave was heated to 75°C.
Polymerization was carried out at 1% while maintaining the temperature between 25Kp/m and 7.45Kp/d.
．． I went for 5 hours. Weight average degree of polymerization 2 molecular weight distribution of the gas-phase polymerized PVC thus obtained: p,,l/po2
and ω were 1760, 4.3, 6.3 and 71% by weight, respectively. The physical properties of the PvC were examined in the same manner as in Example 1, and the melt viscosity was 2.4 x 10' voids, and the gelation time was 11.5 minutes.

Example 6 A 2-ton stainless steel autoclave equipped with a stirrer was charged with ion-exchanged water IK9 in which 1.7 # of partially saponified polyvinyl furfur and 0.7 # of methylcellulose was dissolved and 0.5 g of imbutyryl peroxide, and then the autoclave was degassed. Add 370g of chlorinated vinyl monomer,
Polymerization was carried out at 30°C for 4.7 hours, then 0.49 g of lauroyl peroxide as an initiator was added, the temperature was raised to 71°C, and polymerization was carried out for 1.0 hours. The weight average degree of polymerization of the obtained PVC was 2930. The molecular weight distribution is 4.0. and pu/p
,, = 6.9, ω□ = 66 wt%. The molding processability of the PVC obtained in this manner was examined by examining the gelation time at 180° C. using a Plastucoder for those mixed according to the soft compounding treatment shown in Table 0. As a result, the gelation time was 4.3 minutes. As a comparative example, the degree of polymerization was 2960. As a result of measuring PVC with a molecular weight distribution of 2.7,
The gelation time was 6.7 minutes.

Table C

Claims (2)

[Claims] (1) Vinyl chloride monomer or a mixture of vinyl chloride monomer and other copolymerizable monomers is polymerized in multiple batches in the presence of a polymerization initiator, and the chloride obtained in each batch of polymerization. In the method for producing a polyvinyl chloride composition comprising a vinyl polymer, in the second and subsequent polymerizations, in the presence of the vinyl chloride polymer obtained in the previous polymerization, the vinyl chloride obtained in the first polymerization is The remaining vinyl chloride monomer or mixture is polymerized so that the weight average degree of polymerization is smaller than that of the polymer, and the weight average degree of polymerization of the polyvinyl chloride composition is P-o, and the molecular weight of the polyvinyl chloride composition is When Q is the distribution and ω□ is the proportion of the vinyl chloride polymer obtained in the first polymerization in the polyvinyl chloride composition, Pω > 1000, Q > 2.8, and 65 weight theory≦ω□ , ≦90% by weight. (2) A method for producing a polyvinyl chloride composition, which comprises polymerizing so that the molecular weight distribution Q satisfies Q≧3.5.