JP2014080469A - Method of manufacturing vinyl chloride-based polymer excellent in moldability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a vinyl chloride-based polymer excellent in moldability, more specifically a method of manufacturing a vinyl chloride polymer having low stickiness to a calender roll surface when molding a film or a sheet by calender molding, and excellent in fish eye, transparency and initial coloration of a molded body.SOLUTION: When a vinyl chloride-based monomer mainly containing a vinyl chloride monomer is suspension polymerized in an aqueous medium in a presence of a dispersant and an oil-soluble polymerization initiator, both the oil-soluble polymerization initiator (I) having the 10 hours half-life temperature of 30 to 40°C and the oil-soluble polymerization initiator (II) having the 10 hours half-life temperature of 41 to 60°C are used at a composition ratio of 1:10 to 1:1, and a first step polymerization is conducted at the polymerization temperature of 35 to 44°C till a polymerization conversion ratio of 5 to 20 mass%, then the temperature is increased, and a second step polymerization is conducted at the polymerization temperature of 55 to 80°C. The temperature increasing time is 1% to 20% of total polymerization time.

Description

  The present invention relates to a method for producing a vinyl chloride polymer having excellent moldability. More specifically, when forming into a film or sheet by a calender device, the adhesion to the calender roll surface is low, the gelation time is short, and the formed film or sheet is transparent with little fish eye (FE). The present invention relates to a method for producing a vinyl chloride polymer having excellent properties and initial colorability.

  Vinyl chloride polymers are widely used in various fields such as pipes, flat plates, and sheets because they have good physical and chemical properties and are excellent in economic efficiency. However, on the other hand, it has the disadvantage of being inferior in moldability.

  The vinyl chloride polymer is inferior in moldability because the vinyl chloride polymer has a high melt viscosity, poor fluidity, and is easy to be thermally decomposed. This is based on the fact that it easily adheres to the metal surface of the molding machine.

  Therefore, in the molding process of the vinyl chloride polymer, various molding defects occur due to the adhesion of the molten resin to the metal surface of the molding machine, and the production efficiency decreases. For example, when a sheet of a vinyl chloride polymer is continuously formed by calendering, the sheet of the vinyl chloride polymer becomes difficult to peel off from the calendar roll, and the resulting product sheet deteriorates in appearance, decreases in productivity, or takes a long time. Problems such as difficult processing.

  Therefore, attempts have been made to improve molding processability by adding compounding agents such as lubricants, stabilizers, plasticizers and processing aids to vinyl chloride polymers. In particular, a method of adding an external lubricant such as paraffin, polyethylene wax, ester wax, higher fatty acid, fatty acid amide, etc. is usually adopted when trying to improve the releasability from the metal surface of the molding machine. Yes.

  However, since the external lubricant is generally poorly compatible with the vinyl chloride polymer, the physical properties such as transparency of the resulting molded product are reduced, and when the amount of external lubricant used is increased, Not only does the physical properties of the molded product itself deteriorate, but it also tends to cause molding defects. For example, when calendering, gelation is delayed due to excessive lubricity, plate-out occurs, the surface of the calender roll is contaminated, and the resulting product sheet has the disadvantage that the appearance deteriorates. .

  As a method for solving these molding processability problems, a method is known in which gelation is accelerated by widening the molecular weight distribution of a vinyl chloride polymer. As a method for widening the molecular weight distribution, the polymerization temperature is changed (increased) during suspension polymerization of the vinyl chloride monomer.

  For example, polymerization is carried out at the initial temperature level until a monomer conversion of 10-60% is achieved in the presence of an effective concentration of hot free radical initiated catalyst, the temperature of the system is raised above the initial temperature level, and the polymerization reaction Thus, a vinyl chloride polymer having improved processability is obtained by maintaining this temperature until the process is completed (Patent Document 1). It is also shown that a second hot free radical initiating catalyst is added after the temperature rise. In this method, the viscosity and melting torque of the resulting vinyl chloride polymer are reduced, and the fluidity is good, but the adhesion to the roll surface of the calendar sheet occurs quickly, which is satisfactory in terms of calendar workability. It wasn't.

  Further, the polymerization reaction is carried out while raising the polymerization temperature with time in a period of 50% or more of the whole period during which the polymerization reaction substantially proceeds, and the variation range is in the range of 1 to 20 ° C. A method for producing a vinyl chloride polymer is known (Patent Document 2). In this production method, it is possible to obtain a vinyl chloride polymer having a high bulk specific gravity, a large porosity, and excellent gelling properties and plasticizer absorption properties. In this case, however, the calender sheet adheres to the roll surface. However, it was not satisfactory in terms of calendar workability.

  Furthermore, in the method disclosed in Patent Document 2, the bulk specific gravity and the gelation melting rate increase as the temperature increase range of the polymerization temperature in the polymerization reaction increases. However, if the temperature increase range is increased, heat is generated at the end of the polymerization reaction. However, it has been pointed out that a sufficient polymerization reaction is not performed at the end of the reaction due to a shortage of polymerization initiator and the polymerization reaction is not completed within a predetermined time (Patent Document 3). ). Therefore, in Patent Document 3, two kinds of polymerization initiators are used, and the polymerization temperature is increased with time in a time of 50% or more of the polymerization time. It is proposed to specify the relationship.

  In the method of Patent Document 3, polymerization is sufficiently carried out even at the end of the polymerization reaction, and a vinyl chloride polymer having a large bulk specific gravity and a high gelation speed is obtained. The polymer polymer was not satisfactory in terms of calendar workability because the calendar sheet was quickly adhered to the roll surface.

Japanese Patent Publication No. 49-28910 Japanese Patent Publication No. 03-57121 Japanese Patent Laid-Open No. 07-278207

  In the conventional method for producing a vinyl chloride polymer described above, a viscosity reduction, a torque reduction during melting, and a vinyl chloride polymer excellent in gelling properties can be obtained. Such a vinyl chloride polymer has poor releasability from the calender roll, causing problems such as deterioration in the appearance of the resulting product sheet, reduction in productivity, and difficulty in processing for a long time.

  Accordingly, an object of the present invention is to provide a method for producing a vinyl chloride polymer excellent in molding processability, more specifically, when molding a film or a sheet by calendar molding, the adhesiveness to the calendar roll surface is low. Furthermore, it is an object of the present invention to provide a method for producing a vinyl chloride polymer that has a short gelation time and is excellent in fish eyes, transparency, initial colorability and the like of a molded product.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors use a specific oil-soluble polymerization initiator in a specific combination, set the polymerization temperature in two stages, and control the time taken to increase the temperature. As a result, it was found that a vinyl chloride copolymer having low adhesiveness to the calender roll surface, fast gelation time and excellent fish eyes of the molded product was obtained, and the present invention was completed.

That is, the present invention relates to a chlorination method in which a vinyl chloride monomer or a vinyl chloride monomer mainly composed of a vinyl chloride monomer is subjected to suspension polymerization in an aqueous medium in the presence of a dispersant and an oil-soluble polymerization initiator. A method for producing a vinyl polymer, comprising:
As the oil-soluble polymerization initiator, a composition ratio of an oil-soluble polymerization initiator (I) having a 10-hour half-life temperature of 30 to 40 ° C and an oil-soluble polymerization initiator (II) having a 10-hour half-life temperature of 41 to 60 ° C is 1: 10-1: 1 in combination,
In the first stage polymerization, the polymerization temperature is 35 to 44 ° C., the polymerization conversion is 5 to 20% by mass, and then the temperature is raised over 1% to 20% of the total polymerization time. A method for producing a vinyl chloride polymer, characterized in that polymerization is carried out at a polymerization temperature of 55 to 80 ° C.

  By the production method of the present invention, it is possible to obtain a vinyl chloride polymer having an excellent calendar moldability, which has a fast gelation time, a high apparent density, a small amount of fish eyes, and a small amount of roll adhesion during roll processing. Industrial value is very high.

  The present invention is described in detail below.

  The vinyl chloride polymer in the present invention is a vinyl chloride monomer or a mixture of vinyl chloride monomer and other monomers copolymerizable with the vinyl chloride monomer (hereinafter referred to as these). Is a vinyl chloride homopolymer or a vinyl chloride copolymer obtained by polymerizing a vinyl chloride monomer). The phrase “consisting mainly of vinyl chloride monomer” means containing 50% by mass or more of vinyl chloride monomer.

  Examples of other monomers copolymerizable with vinyl chloride monomer include olefins such as ethylene and propylene, vinyl esters such as vinyl acetate and vinyl stearate, methyl acrylate and methyl methacrylate ( Mention may be made of unsaturated dicarboxylic acid esters such as (meth) acrylic acid esters, maleic acid and fumaric acid, or anhydrides, unsaturated nitriles such as acrylonitrile, and vinylidene chloride compounds such as vinylidene chloride.

  The polymerization of the vinyl chloride monomer in the present invention employs a so-called suspension polymerization method in which the vinyl chloride monomer is suspended and polymerized in a generally known aqueous medium. Specifically, oil-soluble polymerization initiators (I) and (II) having different 10-hour half-life temperatures (hereinafter abbreviated as “HDT”) are used, and the first stage polymerization is performed at a polymerization temperature of 35 to 45 ° C., Preferably 37 to 42 ° C., polymerization conversion 5 to 20% by mass, preferably 6 to 18% by mass, the second stage polymerization is polymerization temperature 55 to 80 ° C., preferably 60 to 75 ° C., from the first stage The temperature raising time to the second stage is 1% to 20% of the total polymerization time. Although the temperature raising time is preferably as short as possible, it is usually difficult to make it less than 1% of the total polymerization time, and there is concern that the polymerization reaction may run away. HDT is a temperature at which half of the oil-soluble polymerization initiator after 10 hours remains when the oil-soluble polymerization initiator is dissolved in toluene, solvesso, paraffin, etc. and maintained at a predetermined temperature. It is.

  In the present invention, the oil-soluble polymerization initiator has a composition ratio of HDT 30-40 ° C (oil-soluble polymerization initiator (I)) and 41-60 ° C (oil-soluble polymerization initiator (II)). : 10 to 1: 1, preferably 1:10 to 1: 2. As the oil-soluble polymerization initiator (I), any one having HDT of 30 to 40 ° C. can be used. For example, 3-hydroxy-1,1-dimethylbutylperoxyneodecanoate (HDT: 38 ° C.) ), Cumyl peroxyneodecanoate (HDT: 36.5 ° C.), peroxides such as isobutyryl peroxide (HDT: 32.7 ° C.), 2,2′-azobis (4-methoxy-2, Diazo compounds such as 4-dimethylvaleronitrile (HDT: 30 ° C.) can be used, and among them, cumylperoxyneodecanoate is preferable. These can be used alone or in combination of two or more.

  As the oil-soluble polymerization initiator (II), any HDT having a temperature of 41 to 60 ° C. can be used without any problem. For example, t-butyl peroxyneodecanoate (DHT: 46.4 ° C.), t-butyl Peroxyneoheptanoate (DHT: 50.6 ° C), t-amyl peroxypivalate (HDT: 54 ° C), t-butyl peroxypivalate (HDT: 54.6 ° C), t-hexylperoxy Examples include peroxides such as pivalate (HDT: 53.2 ° C.), diazo compounds such as 2,2′-azobis (2,4-dimethylvaleronitrile) (HDT: 51 ° C.), t-Hexylperoxypivalate is preferred. These can be used alone or in combination of two or more.

  The total amount of the oil-soluble polymerization initiator (I) and the oil-soluble polymerization initiator (II) is preferably 100 to 1000 ppm, more preferably 200 to 1000 ppm, based on the vinyl chloride monomer charge.

  If it is less than 100 ppm, the polymerization time becomes long and the productivity is lowered. On the other hand, if it exceeds 1000 ppm, the polymerization reaction is difficult to control.

  The composition ratio (weight) of the oil-soluble polymerization initiator (I) and the oil-soluble polymerization initiator (II) is preferably 1:10 to 1: 1. When the composition ratio of the oil-soluble polymerization initiator (I) and the oil-soluble polymerization initiator (II) is less than 1:10, the progress of the first stage polymerization is extremely slow, and the target conversion rate is reached. Time is required and productivity is greatly reduced. On the other hand, if the composition ratio of the oil-soluble polymerization initiator (I) and the oil-soluble polymerization initiator (II) exceeds 1: 1, heat generation at the second stage polymerization temperature is large and it is difficult to keep the polymerization temperature constant. Thus, a vinyl chloride polymer having a desired degree of polymerization cannot be obtained, which is not preferable.

  The dispersant used in the present invention may be a known dispersant used in suspension polymerization of vinyl chloride monomers, such as partially saponified polyvinyl alcohol, vinyl acetate-maleic anhydride copolymer, polyvinyl pyrrolidone, Gelatin, starch, methyl cellulose, hydroxypropyl cellulose and the like can be mentioned, and the amount used is preferably 100 to 2000 ppm with respect to the charged amount of the vinyl chloride monomer.

  The polymerization in the present invention is carried out at a polymerization temperature of 35 to 44 ° C. as the first stage. When the polymerization temperature is lower than 35 ° C., a vinyl chloride polymer having a polymerization degree higher than 3500 is generated. This high degree of polymerization component is poor in meltability, and although adhesion to the roll is suppressed, FE increases, not only the quality as a calendar sheet is lowered, but also the productivity is greatly reduced due to the slow polymerization rate. However, it becomes less practical. On the other hand, when the polymerization temperature is higher than 44 ° C., a vinyl chloride polymer having a polymerization degree lower than 2000 is generated. Since the component having a low polymerization degree is easily melted, the suppression of adhesion to the roll becomes insufficient, and the effect of the present invention is not exhibited.

  Further, the polymerization temperature in the first stage may be changed between 35 to 44 ° C. or constant temperature, but the average degree of polymerization of the vinyl chloride polymer produced during this period is 2000 to 3500. If there is, the effect of this patent is demonstrated. From the viewpoint of controlling the average degree of polymerization of the finally obtained vinyl chloride polymer, it is preferable to keep the polymerization temperature in the first stage constant.

  In the present invention, the first stage needs to be polymerized until the polymerization conversion rate is 5 to 20% by mass. The polymerization conversion referred to here is a value obtained by dividing the weight of the polymer produced up to a certain point by the monomer charge weight. When the polymerization conversion rate is lower than 5% by mass, the effect of suppressing roll adhesion is not exhibited because there are few vinyl chloride polymer components on the high polymerization degree side generated in the first stage. On the other hand, when the polymerization conversion rate exceeds 20% by mass, the effect of suppressing roll adhesion is exhibited, but since the vinyl chloride polymer component on the high polymerization degree side increases, the meltability (gelability) is deteriorated, A lot of FE remains and the quality of the calendar sheet is deteriorated.

  In the present invention, the polymerization temperature is set to 55 to 80 ° C. as the second stage. This polymerization temperature is a temperature that controls the average degree of polymerization of the final vinyl chloride polymer as a target. When this polymerization temperature is lower than 55 ° C., the final vinyl chloride polymer having an average degree of polymerization of 1100 is obtained, the gelation property is inferior, and the effects of the present invention are not exhibited. On the other hand, when the polymerization temperature exceeds 80 ° C., the pressure during the polymerization is increased, which is not preferable because it is necessary to increase the pressure resistance of the polymerization apparatus for producing the vinyl chloride polymer. The polymerization temperature in the second stage may be changed between 55 to 80 ° C. or constant temperature, but the average degree of polymerization of the vinyl chloride polymer produced during this period is 400 to 1000. If there is, the effect of this patent is demonstrated. From the viewpoint of controlling the average degree of polymerization of the finally obtained vinyl chloride polymer, it is preferable to keep the second stage polymerization temperature constant.

  In the present invention, a generally used chain transfer agent can also be used for the purpose of lowering the pressure during polymerization.

  In the present invention, the time required to raise the temperature from the first stage polymerization temperature to the second stage polymerization temperature is set to be within 20% of the total polymerization time. When the temperature rise time exceeds 20% of the total polymerization time, the gelation property is inferior, the effect of the present invention is not exhibited, and the temperature control at the time of temperature rise is difficult, and the average degree of polymerization of the intended final product It will be very difficult to get. Further, as described above, the temperature raising time is preferably as short as possible, but usually it is difficult to make it less than 1% of the total polymerization time, and there is a concern that the polymerization reaction may run away. In the present invention, the “total polymerization time” means that the vinyl chloride monomer is charged into the reactor, the polymerization temperature is set to the polymerization temperature in the first stage, and the temperature is increased from the start of the polymerization reaction. The polymerization temperature is reached at the second stage, and the polymerization is further advanced to reach a predetermined polymerization conversion rate, usually 80 to 90% by mass, until the polymerization reaction is stopped by adding a polymerization terminator. Usually, after the polymerization reaction is stopped, the unreacted monomer is recovered.

  In the present invention, the obtained vinyl chloride polymer has an average degree of polymerization of 600 to 1100. When the average degree of polymerization of the vinyl chloride polymer is less than 600, the roll adhesiveness is inferior, and when it exceeds 1100, the gelation property is inferior as described above, and the effects of the present invention may not be exhibited.

  In addition, additives used in the polymerization, for example, a polymerization regulator, a chain transfer agent, a pH regulator, an antistatic agent, a scale inhibitor and the like can be appropriately added as necessary. A small amount of a surfactant can be added together with the dispersant.

  In the present invention, the resulting vinyl chloride polymer is fast in gelation, has a high apparent density, and has good roll adhesiveness at the time of melting, and therefore has good workability in extrusion molding, injection molding, and calendar molding. In particular, it can be suitably used for calendar molding.

  The method for producing the calender roll sheet of the present invention may be generally known, and the type of calender molding machine is not particularly limited. For example, calendar sheet forming machines such as 6 rolls, upright 4 rolls, L 4 rolls, inverted L 4 rolls, Z 4 rolls, inclined Z 4 rolls, upright 3 rolls, etc. Can be used. Further, the calendar processing conditions are not particularly limited. For example, the temperature of the calendar roll is preferably in the range of 130 to 250 ° C.

  The thickness of the calendar sheet of the present invention is appropriately controlled by setting the clearance of the calendar molding machine, and the thickness is, for example, 30 to 1000 μm, preferably 50 to 500 μm.

  In addition, the calendar sheet of the present invention may be used by laminating with other thermoplastic resin sheets or films. As another thermoplastic resin, an amorphous polyester resin is preferable.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, these do not limit the scope of the present invention at all.

  In Examples and Comparative Examples, average polymerization degree, apparent density, roll adhesiveness, gelation time, and fish eye were evaluated according to the following methods.

(1) Average polymerization degree It measured according to the appendix of JIS K-6720-2: 1999.

(2) Apparent density It measured according to JIS K-7365: 1999.

(3) Gelation time 60 g of compound obtained by stirring and mixing 3 parts by mass of a tin-based liquid stabilizer and 2 parts by mass of a lubricant with respect to 100 parts by mass of a vinyl chloride polymer, Labo Plast Mill manufactured by Toyo Seiki Seisakusho Co., Ltd. It was put into a mixer tester, kneaded at a chamber temperature of 160 ° C. and a roller rotation speed of 40 rpm, and the time until the maximum torque was shown was defined as the gel time.

(4) Roll adhesiveness 4 parts by mass of a dibutyltin malate stabilizer and 1.5 parts by mass of a fatty acid ester lubricant were blended with 100 parts by mass of the vinyl chloride polymer. This compounded composition is kneaded with an 8-inch (diameter: about 20 cm) two rolls (test roll machine manufactured by Kansai Roll Co., Ltd.) having a surface temperature of 185 ° C., and further kneaded for 5 minutes after the compounded composition is wound around the roll. The sheet was taken out. Then, the taken-out sheet | seat was thrown into the roll machine again, and after winding around a roll, it knead | mixed for 5 minutes and took out the sheet | seat. The ease of taking out the sheet from the roll (ease of peeling) when this operation was repeated 5 times was evaluated according to the following criteria.
A: No adhesion (peeling without problems).
○: Slightly sticky (easy peeling)
Δ: Adhesion is large (slightly difficult to peel).
X: Adhesive intense (separation difficult).

(5) Fisheye (FE)
After mixing 40 parts by mass of di-2-ethylhexyl phthalate, 3 parts by mass of a Ca-Zn composite metal soap stabilizer and a small amount of ultramarine, 100 parts by mass of the vinyl chloride polymer, the mixture is kneaded for 3 minutes with a 160 ° C roll. Thereafter, a sheet having a thickness of 50 μm was taken out from the roll. The number in 100 cm ² was counted using unmelted particles having a diameter of 100 μm or more found in this sheet as FE.

Example 1
A stainless steel autoclave with an internal volume of 600 liters equipped with a stirrer and a jacket was charged with 230 kg of pure water and 140 g of polyvinyl alcohol (polymerization degree 2600) with a saponification degree of 80 mol%, and the inside was deaerated with a vacuum pump. Among them, 230 kg of vinyl chloride monomer, 11.5 g of cumyl peroxyneodecanoate (HDT: 36.5 ° C., oil-soluble polymerization initiator (I)) (50 ppm relative to vinyl chloride monomer) and tert -Hexyl peroxypivalate (HDT: 53.2 ° C, oil-soluble polymerization initiator (II)) 69.0 g (300 ppm with respect to vinyl chloride monomer) was charged. Next, the inside of the autoclave was stirred and adjusted to 40 ° C., and the first stage polymerization was started.

  Polymerization was carried out for 200 minutes while adjusting the temperature and amount of hot water passed through the jacket so as to keep the temperature in the autoclave at 40 ° C. The polymerization conversion rate at this time was 10 mass%. Thereafter, the temperature of the hot water passed through the jacket was raised, the temperature inside the autoclave was raised to 66 ° C. over 20 minutes, and this temperature was maintained to continue the second stage polymerization. 420 minutes after the start of the polymerization, the pressure dropped from the maximum value by 270 kPa, so the polymerization was stopped, the unreacted monomer was recovered, and the polymerization was terminated. The resulting slurry was dehydrated and dried to obtain a vinyl chloride polymer. The yield was 82% by mass. The temperature raising time was 4.8% of the total polymerization time.

  The obtained vinyl chloride polymer was evaluated as described above, and the results obtained are shown in Table 1. The obtained vinyl chloride polymer had high apparent density, fast gelation, little sticking to the roll during roll processing, and excellent calendar workability.

(Example 2)
In Example 1, the polymerization was carried out in the same manner as in Example 1 except that the polymerization time in the first stage was 120 minutes and the temperature was raised to 65 ° C. in the second stage. The first stage polymerization conversion was 5%, and the total polymerization time was 380 minutes. The temperature raising time was 5.3% of the total polymerization time.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1. The obtained vinyl chloride polymer had high apparent density, fast gelation, little sticking to the roll during roll processing, and excellent calendar workability.

(Example 3)
In Example 1, 23.0 g of cumylperoxyneodecanoate (100 ppm to vinyl chloride monomer), the first stage polymerization was 150 minutes, the temperature elevation time was 25 minutes, and the second stage polymerization was Polymerization was conducted in the same manner as in Example 1 except that the polymerization temperature was 68 ° C. The first stage polymerization conversion was 18%, and the total polymerization time was 400 minutes. The temperature raising time was 6.3% of the total polymerization time.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The obtained vinyl chloride polymer had high apparent density, fast gelation, little sticking to the roll during roll processing, and excellent calendar workability.

(Example 4)
In Example 1, the polymerization was carried out in the same manner as in Example 1 except that the temperature rising time was 25 minutes, the second stage polymerization temperature was 73 ° C., and the polymerization was stopped when the pressure dropped from the maximum value by 330 kPa. went. The first stage polymerization conversion was 18%, and the total polymerization time was 450 minutes. The temperature raising time was 5.6% of the total polymerization time.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The obtained vinyl chloride polymer had high apparent density, fast gelation, little sticking to the roll during roll processing, and excellent calendar workability.

(Example 5)
In Example 1, when the polymerization temperature in the second stage was 68 ° C. and the temperature rise reached the temperature in the second stage, 27.6 g of 2-mercaptoethanol (chain transfer agent) (120 ppm vs. vinyl chloride monomer) Polymerization was carried out in the same manner as in Example 1 except that the (B) was added. The first stage polymerization conversion was 10%, and the total polymerization time was 440 minutes. The temperature raising time was 4.5% of the total polymerization time.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The obtained vinyl chloride polymer had high apparent density, fast gelation, little sticking to the roll during roll processing, and excellent calendar workability.

(Example 6)
In Example 1, 11.5 g (50 ppm vs. vinyl chloride monomer) of 3-hydroxy-1,1-dimethylbutylperoxyneodecanoate (HDT: 38 ° C.) was used as the oil-soluble polymerization initiator (I). , 69.0 g of t-amyl peroxypivalate (HDT: 54 ° C.) (300 ppm vs. vinyl chloride monomer) was used as the oil-soluble polymerization initiator (II), and the polymerization time in the first stage was 220 minutes. Except for the above, polymerization was carried out in the same manner as in Example 1. The first stage polymerization conversion was 10%, and the total polymerization time was 450 minutes. The temperature raising time was 4.4% of the total polymerization time.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The obtained vinyl chloride polymer had high apparent density, fast gelation, little adhesiveness to the roll during roll processing, and excellent calendar workability.

(Comparative Example 1)
After the same preparation as in Example 1, the polymerization temperature was raised to 64 ° C., and the polymerization was carried out while maintaining that temperature. When the polymerization conversion reached 82%, the same procedure as in Example 1 was performed. The polymerization was stopped. The total polymerization time was 310 minutes.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The resulting vinyl chloride polymer was slow in gelation and had a lot of adhesion to the roll during roll processing, and was poor in calendar workability.

(Comparative Example 2)
In Example 1, polymerization was performed in the same manner as in Example 1 except that the first stage polymerization was performed for 60 minutes and the second stage polymerization temperature was 65 ° C. The first stage polymerization conversion was 3%, and the total polymerization time was 340 minutes. The temperature raising time was 5.9% of the total polymerization time.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The resulting vinyl chloride polymer was slow in gelation and had a lot of adhesion to the roll during roll processing, and was poor in calendar workability.

(Comparative Example 3)
In Example 1, 23.0 g of cumylperoxyneodecanoate (100 ppm to vinyl chloride monomer), the first stage polymerization was 400 minutes, the second stage polymerization temperature was 73 ° C., and the pressure Polymerization was carried out in the same manner as in Example 1 except that the polymerization was stopped at a time when the value of 330 decreased from the maximum value by 330 kPa. The first stage polymerization conversion was 25% by mass, and the total polymerization time was 550 minutes. Further, the temperature raising time was 3.6% of the total polymerization time.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The obtained vinyl chloride polymer had a fast gelation, little adhesion to the roll during roll processing, and was excellent in calendar processability, but had a poor fish eye.

(Comparative Example 4)
In Example 1, the polymerization was conducted in the same manner as in Example 1 except that the first stage was a polymerization temperature of 47 ° C. and the polymerization time was 180 minutes, the polymerization temperature of the second stage was 68 ° C., and the temperature elevation time was 25 minutes. went. The first stage polymerization conversion was 10% by mass as in Example 1, and the total polymerization time was 350 minutes. Further, the temperature raising time was 4.3% of the total polymerization time.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The resulting vinyl chloride polymer was slow in gelation and had a lot of adhesion to the roll during roll processing, and was poor in calendar workability.

(Comparative Example 5)
In Example 1, 46.0 g of cumylperoxyneodecanoate (200 ppm vs. vinyl chloride monomer) and 34.5 g of tert-hexylperoxypivalate (150 ppm vs. vinyl chloride monomer) were used. After 100 minutes of one-step polymerization, the temperature was raised to 68 ° C. over the course of 20 minutes. Immediately after the temperature was raised, control of heat removal became impossible, and the polymerization was immediately stopped. Since no vinyl chloride polymer worthy of evaluation was obtained, evaluation was not performed.

(Comparative Example 6)
In Example 1, the polymerization was carried out in the same manner as in Example 1 except that the temperature raising time was 100 minutes and the second stage polymerization temperature was 68 ° C. The first stage polymerization conversion was 10% by mass as in Example 1, and the total polymerization time was 400 minutes. The temperature raising time was 25% of the total polymerization time.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the results are shown in Table 1. The resulting vinyl chloride polymer was slow in gelation and had a lot of adhesion to the roll during roll processing, and was poor in calendar workability.

(Comparative Example 7)
Polymerization was conducted in the same manner as in Comparative Example 1 except that the polymerization temperature was 67 ° C. Total polymerization time was 330 minutes.

  The obtained vinyl chloride polymer was evaluated in the same manner as in Example 1, and the results are shown in Table 1. Although the obtained vinyl chloride polymer was slightly improved as compared with Comparative Example 1, gelation was slow, adhesion to the roll during roll processing was large, and calendar workability was poor.

(Comparative Example 8)
85 parts by mass of a vinyl chloride polymer having a polymerization degree of 700 (PVC homopolymer TH-700 manufactured by Taiyo PVC Co., Ltd.) and 15 parts by mass of a vinyl chloride polymer having a polymerization degree of 1300 (PVC homopolymer TH-1300 manufactured by Taiyo PVC Co., Ltd.) Dry blending was performed with a Henschel mixer to obtain a vinyl chloride polymer having an average polymerization degree of 805 as a mixture.

  The vinyl chloride polymer obtained as a mixed product was evaluated in the same manner as in Example 1, and the results are shown in Table 1. In the mixed vinyl chloride polymer, gelation was slow and the fish eye was poor. As for the PVC homopolymer used as a raw material, TH-700 had a problem in calendar processability (evaluation Δ), and TH-1300 was a good one although 250 fish eyes were slightly high.

Claims (3)

Manufacture of vinyl chloride polymer, which is a suspension polymerization of vinyl chloride monomer or vinyl chloride monomer mainly composed of vinyl chloride monomer in aqueous medium in the presence of dispersant and oil-soluble polymerization initiator A method,
As the oil-soluble polymerization initiator, a composition ratio of an oil-soluble polymerization initiator (I) having a 10-hour half-life temperature of 30 to 40 ° C. and an oil-soluble polymerization initiator (II) having a 10-hour half-life temperature of 41 to 60 ° C. 10 ~ 1: 1 in combination,
The first stage polymerization is carried out at a polymerization temperature of 35 to 44 ° C. until the polymerization conversion becomes 5 to 20% by mass, and then the temperature is raised over 1% to 20% of the total polymerization time, A method for producing a vinyl chloride polymer, wherein the second stage polymerization is carried out at a polymerization temperature of 55 to 80 ° C.   The method for producing a vinyl chloride polymer according to claim 1, wherein the obtained vinyl chloride polymer has an average degree of polymerization of 600 to 1100.   A calendar roll sheet comprising a vinyl chloride polymer produced by the method for producing a vinyl chloride polymer according to claim 1.