JP2574078C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension polymerization method of a vinyl chloride monomer, and more particularly, to a method having a large bulk specific gravity, an appropriate particle size, and The present invention relates to a production method for producing a high-quality vinyl chloride resin having excellent gelling properties and powder flowability and improved molding processability with high productivity. [0002] Generally, in the suspension polymerization of a vinyl chloride monomer, the monomer is dispersed as oil droplets in an aqueous medium by a surface chemical action of a suspending agent and a mechanical shear action by stirring. The polymerization is started by the polymerization initiator dissolved in the oil droplets and proceeds, but at the same time, the viscosity of the liquid monomer oil droplets increases with the progress of the polymerization, and finally, the resinous polymer particles Is converted to Then, in the process until the conversion in the initial stage of the polymerization reaches about 5%, coalescence and dispersion in units of oil droplets are repeatedly performed, and a basic skeleton of a particle structure is formed at this stage. Polymer particles finally obtained as a vinyl chloride resin are aggregates composed of a plurality of oil droplet units, and the inside thereof is an aggregate of fine particles having voids. [0003] Therefore, in the suspension polymerization of a vinyl chloride monomer, the formulation of the suspending agent such as the type and amount of the suspending agent, the stirring conditions such as the stirring speed and power, and the conversion of the liquid monomer into a resinous The rate of conversion to a polymer, that is, the polymerization conditions such as the polymerization reaction rate are very important factors in determining the particle structure, and these conditions are quality characteristics due to the particle structure of the resin, for example, It is known that particle size, bulk specific gravity, gelling property, powder fluidity, and the like are controlled. Conventionally, in order to increase the processing productivity during extrusion molding of a vinyl chloride resin or to increase the throughput in a batch mixer, the bulk specific gravity is high, the gelling property is excellent, and an appropriate particle size is required. There has been a demand for a resin having excellent powder flowability and molding processability. As a suspension polymerization method for producing a resin meeting such requirements, for example, a polymerization vessel equipped with a reflux condenser is used, and the water / monomer ratio at the time of initial charging is set to 0.8 to 1.0. A method of adding water during polymerization (Japanese Patent Publication No. 3-4561), a method of adding a monomer during polymerization (JP-A-50-97679), and a method of increasing the polymerization temperature during polymerization (JP-A-50-97679). 6
No. 1-207410), but these methods are insufficient in the effect of increasing the bulk specific gravity, and are coarsened due to insufficient suspension stability of the polymerization system. There were problems such as complicated polymerization operations. [0005] As a suspension polymerization method relating to a suspension agent formulation, many methods using a combination of a plurality of kinds of partially saponified polyvinyl acetate and a cellulose derivative have been proposed. For example, JP-B-63-39606, JP-B-1-27088, JP-B-2-22081, JP-B-2-62121, JP-A-61-141703, JP-A-61-141703,
2-260803, JP-A-62-263206, JP-A-63-156809
And JP-A-63-264611 and JP-A-63-275606. [0006] However, in the formulations disclosed in these prior arts, although the effect of increasing the bulk specific gravity is certainly recognized, the effect is insufficient, or other effects such as particle size, gelling property, powder fluidity, etc. However, it is not satisfactory as a method for stably obtaining a resin excellent in molding processability with high productivity. The inventors of the present invention have conducted intensive studies to solve the above-mentioned drawbacks. As a result, the present inventors have used a specific suspending agent and a suspending aid in a specific weight ratio, Control the stirring power of the
By completing the polymerization within the time, it is possible to obtain a vinyl chloride polymer with high bulk specific gravity, excellent gelling properties, and with appropriate particle size and improved powder flowability and moldability with high productivity. They have found that they can be manufactured, and have completed the present invention. That is, an object of the present invention is to provide an improved method for producing a high quality vinyl chloride polymer with high productivity. [0008] The above and other objects of the present invention According to an aspect of, upon suspension polymerization in an aqueous medium a vinyl chloride monomer in the presence of an oil-soluble polymerization initiator, stirrer and reflux condenser A vessel is installed, and a cooling medium passage is provided inside the polymerization vessel body.
Using internal volume 40 m ³ or more inner jacket type large-sized polymerization vessel, (A) selected from the group consisting of average saponification degree 65-95 mol% of partially saponified polyvinyl acetate and hydroxypropylmethylcellulose least one A suspending agent, and (B) partially saponified polyvinyl acetate and HL having an average degree of saponification of 15 to 55 mol%.
At least one suspension aid selected from the group consisting of nonionic surfactants having a B value of 2 to 10 has a weight ratio of (A) / (B) of 0.5 to 20. in combination, and the polymerization begins conversion rate controls the net stirring power per liquid content 1 m ³ of the polymerization vessel in the period until at least 5% 1.0~2.0kW / m ^3, a reflux condenser as By the most
It is achieved by controlling the large heat removal ratio to less than 50% to carry out the polymerization and completing the polymerization within 6 hours. Hereinafter, the present invention will be described in detail. In the present invention, as the monomer copolymerizable with vinyl chloride, for example, alkyl vinyl esters represented by vinyl acetate, alkyl vinyl ethers represented by cetyl vinyl ether, ethylene, α-monoolefins such as propylene, Such as methyl acrylate, methyl methacrylate, etc.
Examples thereof include alkyl (meth) acrylates, vinylidene chloride, styrene, and the like, but are not limited thereto as long as they copolymerize. [0010] The suspending agent (A) used in the present invention is at least one selected from the group consisting of partially saponified polyvinyl acetate having an average degree of saponification of 65 to 95 mol% and hydroxypropylmethylcellulose. When this is selected from partially saponified polyvinyl acetate, those having a saponification degree of 70 to 90 mol% and an average polymerization degree of 700 to 3000 are preferred. When selected from hydroxypropyl methylcellulose, those having a methoxy group content of 25 to 30% by weight, a hydroxypropoxy group content of 4 to 12% by weight, and a viscosity of 2% by weight aqueous solution at 20 ° C. of 40 to 60 centipoise are preferred. . The suspending agent (A) is a water-soluble component, and has a function of regulating the viscosity and the aggregation state of particles by its dispersing effect and suspension protecting effect. On the other hand, the component (B) used in the present invention is insoluble or hardly soluble in water, and has a low surface activity even when used for suspension polymerization in an aqueous medium. It is generally called a suspension aid, an auxiliary suspension, a secondary suspension or the like. In the present invention, this is called a suspension aid. The suspending aid (B) used in the present invention is selected from the group consisting of partially saponified polyvinyl acetate having an average degree of saponification of 15 to 55 mol% and a nonionic surfactant having an HLB value of 2 to 10. At least one selected compound. When this is selected from partially saponified polyvinyl acetate, the degree of saponification is 30 to 50 mol% and the degree of polymerization is 200 to 800.
Are preferred. On the other hand, examples of nonionic surfactants having an HLB value of 2 to 10 include sorbitan monolaurate, sorbitan monopalmitate, sorbitan (mono, di, tri) stearate, sorbitan fatty acid esters such as sorbitan monooleate, and stearin. Examples include glycerin fatty acid esters such as acid monoglyceride and oleic acid monoglyceride, but are not limited thereto. However, when the suspension aid (B) is selected from the above surfactants, sorbitan fatty acid esters are preferred, and sorbitan monostearate is particularly preferred. The suspending aid (B) is an oil-soluble component, and is presumed to have an action of dissolving in monomer oil droplets and preventing aggregation of fine polymer particles deposited inside and on the surface of the oil droplets. But,
Since a polymer rich in internal voids and having a small number of skin layers can be obtained, there is an effect of improving fish eye, gelling property at the time of molding and plasticizer absorption. In the present invention, the suspending agent (A) and the suspending aid (B) are used as the suspending agent system.
), At least one of each selected from both groups is used in combination, and the weight ratio (
A) / (B) is set to 0.5 to 20, preferably 1 to 10. If the ratio is less than 0.5, the bulk specific gravity of the resin decreases, and the fine powder in the product resin increases to impair the powder fluidity. On the other hand, if this value exceeds 20, the gelling properties of the resin will deteriorate, so that the object of the present invention cannot be achieved. The amount of the suspending agent (A) used is usually in the range of 0.03 to 0.08 parts by weight per 100 parts by weight of the monomer. In carrying out the present invention, first, a monomer, water, a polymerization initiator, and the above-mentioned suspending agent system are charged into a polymerization vessel degassed in advance according to a conventional charging method, and a heating medium is placed in a jacket of the polymerization vessel. The polymerization is started by raising the content of the polymerization vessel to a predetermined polymerization temperature while stirring, by means such as circulating the polymer. In the present invention, the conversion is at least 5% from the initiation of the polymerization, preferably Is the time to reach 10-30%,
That is, until the basic skeleton of the polymer particle structure is formed, the content liquid 1 of the polymerization vessel is used.
The net stirring power per m ³ is 1.0-2.0 kW / m ³ , preferably 1.2-1.
It is essential to control to 6 kW / m ³ . When this value is less than 1.0 kW / m ³ , even when the above-described suspending agent system is used, the polymer particles are coarsened, and the porosity is impaired, and the gelling property is reduced. I do. On the other hand, if it exceeds 2.0 kW / m ³ , there is a disadvantage that not only the bulk specific gravity decreases, but also the particle size becomes fine or coarse particles are generated depending on other polymerization conditions. The stirring power after the conversion reaches 5% is not particularly limited as long as the inside of the polymerization vessel is uniformly stirred. A method for controlling the stirring power of the polymerization vessel is described in detail in, for example, “Chemical Engineering Association, edited by Chemical Engineering Handbook, 3rd revised edition, pp. 1065-1115, 1968, Maruzen Co., Ltd.”. As described above, by using an empirical formula or a diagram representing the relationship between the Reynolds number Re and the power number Np of the stirring system for the stirring devices of various shapes, or by actually measuring the power under certain stirring conditions. Experimentally determining Np as a constant,
The power can be arbitrarily adjusted by changing the rotation speed of the stirring blade. That is, the density of the contents of the polymerization vessel is ρ (kg / m ³ ), and the viscosity coefficient is μ (kg / m ³ ).
m · sec), the rotation speed of the stirring blade is n (1 / sec), the blade span is d (m), the gravity conversion coefficient is gc (kg · m / kg · sec ² ), and the speed reduction mechanism and shaft seal are used. Assuming that the net stirring power that does not include the loss of P is P (kg / m · sec), Re and Np are defined by Re = ρnd ² / μ Np = P · gc / ρn ³ d ⁵ , respectively. Np can be determined from known literature or experiments. The value of Np of a stirrer of a large polymerization vessel generally employed in a suspension polymerization method of a vinyl chloride monomer is in a range of about 0.2 to 2. V (m ³
), The net stirring power Pv (kW / m ³ ) per unit volume of the polymerization vessel can be calculated according to the following equation. ^{Pv = Np · ρn 3 d 5} · / 102 · V · gc Therefore, when adjusting the net stirring power with a specific stirring device, since power is proportional to the cube of the rotational speed of the stirring blade, the rotation Power can be controlled by changing the number. The shape of a stirring device such as a stirring blade used in the present invention and a baffle used if desired is not particularly limited, and a conventional suspension weight method of a vinyl chloride monomer is generally used. Known stirring devices that have been employed can be used, and examples of the stirring blades include a turbine blade, a fan turbine blade, a Faudler blade, and a blue margin blade, and a Faudler blade is preferable. , A pipe type, a D type, a loop type, and an E type (finger type) are exemplified, and a pipe type, a D type, and an E type baffle are preferable. These stirring blades and baffles may be those commonly used in the polymerization of vinyl chloride. For example, the aforementioned Handbook of Chemical Engineering or Koji Saeki: Polymer Production Process, pp. 157-159, 1
971, Industrial Research Committee ". Further, in carrying out the present invention, it is possible to complete a polymerization reaction within 6 hours, which usually takes more than 6 hours in a large-scale polymerization vessel having an internal volume of 40 m ³ or more which has been conventionally employed on an industrial scale. Required. By performing such a high-speed polymerization, the conversion rate from the liquid monomer to the resinous polymer is increased, the frequency of separation and dispersion of oil droplets, and the aggregation of fine particles generated inside the oil droplets in this process. It is presumed that the state is affected, but polymer particles having a high bulk specific gravity can be obtained. In addition, the production of fine particles that inhibit the fluidity of the powder can be suppressed, and there is an advantage that the handleability of the resin during molding is improved. If the time until the completion of the polymerization exceeds 6 hours, the object of the present invention cannot be achieved because the bulk specific gravity and the powder fluidity decrease. In the present invention, the time until the completion of polymerization, that is, the polymerization time, is defined as the time from the time when the internal temperature of the polymerization vessel reaches a predetermined polymerization temperature by a temperature raising operation or the like after the completion of charging of each component such as a monomer. After the pressure in the polymerization reactor has been changed for a while at the natural pressure at the polymerization temperature, the pressure starts to drop as the unreacted monomer decreases, and the time until the drop reaches ² kg / cm ² is defined. The polymerization time in the present invention is preferably 3 to 6 hours from the viewpoint of safety such as temperature control and pressure control of the polymerization vessel. In the present invention, examples of a method for completing the polymerization include a method of adding a polymerization inhibitor and a method of recovering an unreacted monomer from a polymerization vessel. As is known, the polymerization time can be adjusted by the amount of the polymerization initiator used, and the polymerization time can be shortened by increasing the amount of the polymerization initiator. In the present invention, the initiator used to complete the polymerization within 6 hours may be any of those conventionally used in the suspension polymerization method of a vinyl chloride monomer, and is not particularly limited. , 4,4-Trimethylpentyl-2-peroxyneodecanoate, di-2-
Ethylhexyl peroxy dicarbonate, diethoxyethyl peroxy dicarbonate, α-cumyl peroxy neodecanoate, t-butyl peroxy neodecanoate, t-butyl peroxy pivalate, 3,5,5-trimethylhexa Organic peroxides such as noyl peroxide and acetylcyclohexylsulfonyl peroxide; and azo compounds such as α, α′-azobisisobutyronitrile and α, α′-azobis-2,4-dimethylvaleronitrile. And one or a mixture of two or more of these are used. However, it is preferable to use an initiator having a perester structure having a 10-hour half-life temperature of 34 to 50 ° C. in an amount of 50% or more of the total initiator amount used for the polymerization. Although the amount of the initiator used varies depending on the type of the initiator and the polymerization temperature, it is usually 0.02 per 100 parts by weight of the monomer.
To 1 part by weight. [0023] A large amount of reaction heat is generated when a high-speed polymerization is performed within 6 hours according to the present invention using a large-scale polymerization vessel of an industrial scale having an internal volume of 40 m ³ or more. inner jacket type polymerization apparatus described in KOKOKU No. 3-4249, i.e. Runode using a polymerization vessel with improved heat transfer performance by providing a passage of chilling medium into the polymerization vessel body inner surface, the temperature control of the polymerization vessel It becomes easy, and there is no adverse effect such as foaming of the slurry and reduction in suspension stability due to heat removal. As the inner jacket type polymerization vessel, those having a performance of a total heat transfer coefficient of 700 kcal / m ² · hr · ° C. or more at the time of polymerization are preferable. [0024] Ru with a reflux condenser carrying out the present invention, performs heat removal the maximum heat removal rate by the reflux condenser during the polymerization as less than 50%. Here, the ratio of heat removal by the reflux condenser is a ratio of the amount of heat removal by the reflux condenser to the amount of heat generated by the polymerization reaction. If this ratio exceeds 50%, the polymer adheres and accumulates on the heat transfer surface of the reflux condenser due to foaming of the slurry. It is presumed that the polymerization system is violently stirred when vaporized from the inside, but the suspension stability is impaired and coarsened, or the particle shape becomes irregular and it becomes impossible to obtain a spherical resin, There is a disadvantage that the powder fluidity and the bulk specific gravity are reduced. The structure of the reflux condenser is not particularly limited, but generally a multi-tube reflux condenser is exemplified. Any known method can be used for the reflux condenser, but the maximum heat removal rate is controlled to less than 50%. The polymerization is usually carried out at a temperature of 40 to 70 ° C., and a chain transfer agent such as a mercaptoalkanol or an alkyl thioglycolate, a pH adjuster, or a polymerization inhibitor may be used, if desired. . The water may be preheated or degassed. The charged amounts, the number of parts, and other polymerization conditions of these components may be conventional conditions conventionally used in vinyl chloride polymerization, and are not particularly limited. As described above, according to the present invention, a specific suspending agent and a suspending aid are used in combination at a specific weight ratio, and further, a stirring power and a polymerization reaction rate which are structural controlling factors of the polymer particles. By controlling to a specific range, it is possible to obtain a vinyl chloride resin excellent in molding processability such as particle size, bulk specific gravity, gelling property, powder fluidity, and can increase polymerization productivity. Problems that were difficult to achieve with conventional technology can be solved,
Very useful from an industrial point of view. EXAMPLES The present invention will be described more specifically with reference to the following examples. The percentages and parts in Examples and Comparative Examples are based on weight unless otherwise specified. The physical properties of the vinyl chloride resin were measured by the following methods. (1) Average Particle Diameter The average particle diameter was shown as a 50% passage diameter by sieve analysis using a JIS standard wire mesh. (2) Coarse-grain fraction [0029] According to the sieve analysis of (1) above, the ratio is shown as a ratio remaining in a 60-mesh wire net. (3) Bulk specific gravity The values are shown as values measured according to the method specified in JIS K6721. (4) Powder Fluidity The time required for the entire amount of 120 ml of the vinyl chloride resin to fall from the bulk specific gravity measurement hopper specified in JIS K6721 is shown. (5) Gel Time Using a Labo Plast Mill manufactured by Toyo Seiki Seisaku-sho, and setting the temperature of the jacket to 190 ° C.
100 parts (65 g) of vinyl chloride resin, 1 part of lead stearate,
After adding 2.5 parts of tribasic lead sulfate and 0.3 parts of dibasic lead stearate and preheating for 3 minutes, kneading is performed while rotating the roller head at 30 rpm, and the kneading torque is stabilized and a constant value is obtained. The time to show is shown. Experiment Nos. 1 to 3 (Example) and 4 (Comparative Example 1) A multi-tube reflux condenser having a heat transfer area of 80 m ² was connected to the gas phase of the polymerization vessel, and the blade span 1
. After degassing a 3.2 m diameter, 45 m ³ inner jacket stainless steel polymerization vessel equipped with four 7 m Faudler-type retreat stirrers and four pipe baffles with an outer diameter of 0.22 m, a vinyl chloride monomer was added. 100 parts (17.0 tons), 110 parts of water, 0.050 part of partially saponified polyvinyl acetate having a saponification degree of 88 mol% and an average degree of polymerization of 2400 as a suspending agent, and sorbitan mono as a suspending aid Stearate 0.05
0 parts and 0.05 parts of 2,4,4-trimethylpentyl-2-peroxyneodecanoate as a polymerization initiator were charged, and the number of revolutions of a stirring blade was controlled at 112 rpm, and the contents of the polymerization vessel were stirred. The product was heated to a temperature of 57 ° C. to initiate polymerization. Simultaneously with the start of the polymerization, cooling water is passed through a reflux condenser to remove the heat of the polymerization reaction.
The polymerization was started and the polymerization was continued while maintaining the internal temperature at 57 ° C. by controlling the maximum heat removal rate by the reflux condenser to the value shown in Table 1, and the polymerization was initially 8.7 kg / cm ² When the pressure of ６ dropped to 6.7 kg / cm ² , unreacted monomers were recovered from the polymerization vessel to complete the polymerization. Next, the content of the polymerization vessel was discharged and dehydrated and dried to obtain a vinyl chloride resin. The net stirring power Pv is 1.5 kW /
m ³ , but thereafter gradually increased with the progress of polymerization, and reached 1.6 kW / m ³ when the polymerization conversion reached 5%. Polymerization time (from the point when the polymerization temperature is reached,
The time until the completion of the above polymerization) was 4.3 hours, and the conversion at the completion of the polymerization was 85%.
Met. Table 1 shows the results of Experiment Nos. 1 to 4 in comparison. [Table 1 ]

Claims (1)

Claims 1. An oil-soluble polymerization initiator comprising a vinyl chloride monomer selected from a vinyl chloride monomer or a mixture of vinyl chloride and a monomer copolymerizable with vinyl chloride. At the time of suspension polymerization in an aqueous medium in the presence of a stirrer and a reflux condenser, a cooling medium passage is provided on the inner surface of the polymerization vessel main body.
Using internal volume 40 m ³ or more inner jacket type large-sized polymerization vessel, (A) selected from the group consisting of average saponification degree 65-95 mol% of partially saponified polyvinyl acetate and hydroxypropylmethylcellulose least one A suspending agent, and (B) partially saponified polyvinyl acetate and HL having an average degree of saponification of 15 to 55 mol%.
At least one suspension aid selected from the group consisting of nonionic surfactants having a B value of 2 to 10 has a weight ratio of (A) / (B) of 0.5 to 20. in combination, and the polymerization begins conversion rate controls the net stirring power per liquid content 1 m ³ of the polymerization vessel in the period until at least 5% 1.0~2.0kW / m ^3, a reflux condenser as By the most
A suspension polymerization method for a vinyl chloride monomer, wherein polymerization is carried out while controlling a large heat removal ratio to less than 50%, and the polymerization is completed within 6 hours.