JPH0573456B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to an aqueous emulsion of an organic peroxide. More specifically, the present invention relates to an aqueous emulsified organic peroxide that has good storage stability, low viscosity at low temperatures, and good initial fluidity, and is therefore easy to handle during production and use. This aqueous emulsified organic peroxide is useful as a polymerization initiator suitable for polymerization and copolymerization of ethylenically unsaturated monomers, particularly vinyl halide monomers. <Prior art> Suspension or emulsion polymerization of ethylenically unsaturated monomers usually uses a protective colloid agent and/or a surfactant to obtain a polymer with a desired particle size, and to cause a polymerization reaction. This is done by using a polymerization initiator. Recently, in order to improve productivity when polymerizing ethylenically unsaturated monomers and to prevent environmental pollution due to the toxicity of residual and waste monomers, polymerization equipment has been increased in size or production equipment has been automated and continuously operated. At the same time, the polymerization reaction system is closed. As a polymerization initiator suitable for such purposes, organic peroxides emulsified with water are easier to handle than conventionally used solvent-diluted organic peroxides, and are also safer. There is a tendency to like it because there is. In recent years, aqueous emulsions of various organic peroxides have been proposed in response to the above requirements. For example, JP-A-56-139509 discloses an aqueous emulsion organic peroxide containing an organic peroxide, a surfactant, a protective colloid agent such as polyvinyl acetate, and a water-soluble alcohol. Furthermore, JP-A-61-130315 discloses an aqueous emulsion containing an organic peroxide, a nonionic surfactant, polyvinyl acetate having an average degree of polymerization of 600 or less and a degree of saponification of 60 mol% or more, and a water-soluble alcohol. Peroxides are disclosed. This method involves producing an aqueous emulsion of an organic peroxide containing a highly water-soluble protective colloid prior to suspension polymerization or copolymerization of vinyl chloride. Therefore, it does not need to have a low viscosity at low temperatures and be stable over a long period of time. Further, JP-A-62-86005 discloses an aqueous emulsion organic peroxide containing an organic peroxide, polyvinyl acetate having a degree of saponification of 5 to 70 mol %, and a water-soluble alcohol. It is known that such polyvinyl acetate is specified by the average degree of polymerization and saponification degree, but in this case,
For example, even if the average degree of polymerization and degree of saponification are the same, they exhibit completely different physical properties depending on how the hydroxyl groups and acetyl groups are arranged in the backbone polymer. Furthermore, the physical properties of the aqueous emulsified organic peroxides containing the peroxides also differ greatly. <Problems to be Solved by the Invention> These known aqueous emulsified organic peroxides have the following drawbacks. That is, the aqueous emulsified organic peroxide described in JP-A-56-139509 has a high viscosity and poor initial fluidity. Sometimes, when the proportion of the oil phase in the aqueous emulsified organic peroxide is increased, the emulsion becomes extremely viscous. Therefore, it is inconvenient to handle during manufacture, use, or transport by pump. At that time, if the amount of surfactant or protective colloid agent used is reduced in order to lower the viscosity, stability will be significantly impaired. Also, JP-A-61-130315 and JP-A-62-
Although the aqueous emulsion-forming organic peroxide described in Japanese Patent No. 86005 can lower the viscosity, it is not sufficiently stable and is inconvenient for practical use. Furthermore, even if the viscosity of the aqueous emulsified organic peroxide is low when it is produced, if it is stored at a temperature of, for example, -15°C, the viscosity increases over time and the fluidity becomes poor. The drawback was that so-called thixotropy occurred. <Means for Solving the Problems> The present inventors have developed an aqueous emulsified organic peroxide that overcomes the drawbacks of the prior art described above, that is, it has a low viscosity at low temperatures and does not increase in viscosity over time during storage. As a result of intensive research aimed at developing an aqueous emulsion-forming organic peroxide useful as a polymerization initiator for the polymerization or copolymerization of ethylenically unsaturated monomers that has good initial fluidity and good storage stability, By using a combination of a specific polyvinyl acetate and a specific nonionic surfactant, the viscosity of the emulsion is extremely low, the viscosity does not increase over time during storage, the initial fluidity is good, and the storage stability is excellent. The present invention was completed based on the knowledge that the invention was good. That is, the present invention provides sorbitol fatty acid ester, sorbitan fatty acid ester, and sorbite fatty acid ester, which are composed of fatty acid esters of sorbitol, sorbitan, and sorbite, each having a carbon number of 10 to 22, with a weight percentage of 30% or less, 40% or less, respectively. 50% or less, and its hydroxyl value is 60~
230, a partially saponified polyvinyl acetate with a degree of saponification of 50 to 95 mol%, an average degree of polymerization of 10 to 600, a block characteristic of 0.7 or less, an organic peroxide, and a freezing point depressant. The present invention relates to an aqueous emulsified organic peroxide contained as a substantial main component and an initiator for suspension polymerization or copolymerization of an ethylenically unsaturated monomer comprising the aqueous emulsified organic peroxide. Next, each component of the aqueous emulsified organic peroxide of the present invention will be explained. (a) Nonionic surfactant This nonionic surfactant is sorbitol,
It is a mixture of primarily mono-, di-, and tri-fatty acid esters made from sorbitol derivatives such as sorbitan and sorbide. Here, the fatty acid has the general formula

[Formula] (where R=C _o H _2o+1 , C _o H _2o-1 , C _o H _2o-3 , C _o H _2o-5 , n=9
It has the structure shown in ~21). Specifically, the fatty acids include linear and branched saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and isostearic acid; monoene unsaturated fatty acids such as oleic acid and elaidic acid; Polyene unsaturated fatty acids such as rheostearic acid, linolenic acid, oxygenated fatty acids such as silinoleic acid, and corn oil fatty acids, olive oil fatty acids,
There are fatty acids from natural sources such as rice bran oil fatty acids, safflower oil fatty acids, and tall oil fatty acids. In addition, the ratio of sorbitol fatty acid ester, sorbitan fatty acid ester, and sorbide fatty acid ester is 30% or less, 40% or less, and 50% by weight.
Below, preferably 1-30%, 42-90%, 3-30%
50%, and the hydroxyl value of the mixture of nonionic surfactants must be in the range of 60 to 230. Anything outside the above range will result in poor stability. Here, the hydroxyl value is the number of mg of potassium hydroxide required to neutralize acetic acid bound to the acetylated product obtained from 1 g of sample oil. The proportion of the nonionic surfactant in the aqueous emulsion organic peroxide is 0.1 to 10.
% by weight, preferably 0.5 to 5% by weight. If it is less than 0.1% by weight, the stability is insufficient;
Moreover, if it exceeds 10% by weight, not only will the viscosity become too high, but it will also be economically disadvantageous. In addition, the nonionic surfactant may be a general nonionic surfactant, such as propylene glycol fatty acid ester, surfactant, etc., as long as it does not significantly impair the physical properties of the aqueous emulsified organic peroxide or the polymer obtained using the same. It may also contain a nonionic surfactant containing a sugar fatty acid ester or a polyethylene oxide group. (b) Partially saponified vinyl acetate The partially saponified polyvinyl acetate used as a protective colloid in the present invention has a degree of saponification of 50 to 95 mol%.
The average degree of polymerization is 10 to 600, and the block characteristic is 0.7 or less. Here, the block character was calculated by the method shown in Moritani et al. Macromolecules vol. 10, pp. 532-535 (1977). First, a 10% aqueous solution of partially saponified polyvinyl acetate is prepared. Among the methylene protons in the ¹³ C-NMR spectrum, calculate the peak area of those that have both a hydroxyl group and an acetyl group on the adjacent carbon atom as a ratio (A) to the total methylene protons. Next, the value and
Molar fraction of vinyl alcohol, which is a polymerized unit (B)
and the mole fraction (C) of vinyl acetate, the block characteristic (η) was determined by the following formula. η=A/2×B×C The value of this block character shows how the hydroxyl groups and acetyl groups are arranged in the backbone polymer. This shows that there are many The smaller the block character is, the more preferable it is; if it is larger than 0.7, the stability of the aqueous emulsified organic peroxide is insufficient and the initial fluidity is also poor. Furthermore, the degree of saponification is 50 to 90 mol%. 50 mol%
Even if it is smaller than 90 mol%, the stability of the aqueous emulsified organic peroxide deteriorates, but it is preferably 70 to 90 mol%. Moreover, the average degree of polymerization is 10-600. If it is smaller than 10, the stability of the aqueous emulsified organic peroxide will be poor. On the other hand, if it is greater than 600, the viscosity will not be low at low temperatures and the initial fluidity will also be poor. Commercially available partially saponified polyvinyl acetate included in the present invention includes, for example, Unitika Chemical Co., Ltd.
UMR-30H, UMR-20H, UMR- manufactured by Co., Ltd.
10H, UMR−30M, UMR−20M, UMR−
10M, B-05, B-03 manufactured by Denki Kagaku Kogyo Co., Ltd.
Examples include LG-05 manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd. Table 1 shows the physical properties of these commercially available products.

【table】

[Table] The type and amount of partially saponified polyvinyl acetate are appropriately selected depending on the type of organic peroxide and desired viscosity. Moreover, it may be a mixture of two or more types. The content in the aqueous emulsified organic peroxide is 0.1 to 10% by weight, and is preferably 0.2 to 5% by weight, since too little will result in poor storage stability, and too much will be economically disadvantageous. (c) Organic peroxide The organic peroxide used in the present invention is usually one or more organic peroxides that have a half-life of 10 hours at a temperature of 75°C or lower and a freezing point of 0°C or lower. be. In this case, the present invention also includes a mixture organic peroxide in which the freezing point of the mixture of the organic peroxide and an organic peroxide having a freezing point of 0°C or higher is 0°C or lower. Specifically, the organic peroxides include di(n-propyl)peroxydicarbonate, di(isopropyl)peroxydicarbonate, di(sec-butyl)peroxydicarbonate, di(capryloxydicarbonate),
Di(2-ethylhexyl) peroxydicarbonate, di(2-ethoxyethyl) peroxydicarbonate, di(methoxyisopropyl)
peroxydicarbonates such as peroxydicarbonate, peroxyesters such as t-butylperoxy-2-ethylhexanoate, t-butylperoxypivalate, t-butylperoxyneodecanoate, cumylperoxyneodecanoate; Propionyl peroxide, diisobutyl peroxide, di(3,
diacyl peroxides such as 5,5-trimethylhexanoyl) peroxide. Further, in the present invention, an organic peroxide diluted with an organic solvent can also be used in order to improve the thermal stability of the organic peroxide or to lower the freezing point. Examples include benzene, toluene, aliphatic hydrocarbons, and plasticizers such as dithylphthalate and dioctyl phthalate. When used, the content of organic solvent is 40% in the aqueous emulsion of organic peroxide.
Within % by weight. In the organic peroxide aqueous emulsion of the present invention, the content of the organic peroxide is usually 5 to 80%.
% by weight, and if it is too small, transportation costs will increase, which is economically unfavorable. Practically preferred is 10 to 65% by weight. (d) Freezing point depressant The freezing point depressant used in the present invention may be any of those previously used for the purpose of freezing point depressants in aqueous emulsions of organic peroxides. In particular, lower alcohols are preferred.
For example, methyl alcohol, ethyl alcohol,
ethylene glycol, diethylene glycol,
Contains triethylene glycol and glycerin. The content is usually 2% to 30% by weight. The aqueous emulsified organic peroxide of the present invention is produced by a known method. Specifically, all conventional methods for producing aqueous emulsions can be used, but generally the partially saponified polyvinyl acetate and freezing point depressant are dissolved or dispersed in the aqueous phase, while the organic peroxide is interfacially dissolved as an oil phase. Dissolve or disperse the active agent. Then, the oil phase is mixed with the water phase. Furthermore, it is emulsified using a homogeneous disperser. The product obtained in this way has excellent properties in terms of safety and safety because it uses water as a continuous phase. The organic peroxide aqueous emulsion of the present invention may contain inorganic salts such as sodium chloride in addition to the above-mentioned components to an extent that does not affect storage stability. To produce the aqueous emulsified organic peroxide of the present invention, for example, a paddle-type, propeller-type, or turbine-type mechanical stirrer, a colloid mill,
Conventionally known devices such as a homogenizer, high-speed shearing device, line mixer, and ultrasonic homogenizer can be used. By using these devices to form an emulsion with an average particle size of 10 μm or less, it is possible to make it extremely stable. The aqueous emulsified organic peroxide of the present invention is useful as a polymerization or copolymerization initiator for ethylenically unsaturated monomers. Applicable monomers include vinyl halides such as vinyl chloride, vinyl halide monomers such as vinylidene halide, vinyl ethers, esters of acrylic acid or methacrylic acid, aromatic vinyls such as styrene,
Examples include esters of maleic acid or fumaric acid, ethylene, and vinyl acetate. And particularly preferred is vinyl chloride. When performing suspension polymerization, for example, water, a dispersion aid, and the above monomer are charged into a polymerization vessel, and then an aqueous emulsion-forming organic peroxide is charged, and the quality is improved by polymerizing by stirring and heating. An excellent polymer is obtained. Methods for charging the aqueous emulsified organic peroxide include diluting it with water to an appropriate viscosity and charging it by pumping. At that time, the amount of the aqueous emulsion-forming organic peroxide used is within the usual usage range. <Effects of the Invention> The aqueous emulsified organic peroxide of the present invention has various advantages. That is, it has a low viscosity at low temperatures and does not increase in viscosity over time during storage.
In addition, the initial fluidity at low temperatures is good because the applied viscosity does not increase even when the shear rate decreases. It is also stable against vibration and has good storage stability.
It is extremely easy to handle and transport during use. It is particularly effective compared to conventional methods when the proportion of the oil layer in the aqueous emulsion is as high as 50% by weight or more. Furthermore, when used as a polymerization initiator for suspension polymerization or copolymerization of ethylenically unsaturated monomers, it is easier to handle because it has better fluidity than conventional polymerization initiators. <Example> Next, an example and a comparative example will be given and explained, but all are for illustrative purposes and the present invention is not limited to them only. Examples 1 to 10 and Comparative Examples 1 to 3 Aqueous emulsified organic peroxides having the formulations shown in Table 2 were produced as follows. First, it was equipped with a propeller blade type stirring device and a thermometer.
Water, a freezing point depressant, and partially saponified vinyl acetate (protective colloid) were placed in a 500 ml three-necked flask. After dissolution, an aqueous solution at about 10° C. was obtained by cooling. On the other hand, a solution obtained by mixing a nonionic surfactant and an organic peroxide was dropped into the aqueous solution while stirring. Stirring was continued for 30 minutes after the dropwise addition, and a milky white aqueous emulsion of organic peroxide was obtained.

【table】

【table】

[Table] Using the aqueous emulsified organic peroxides shown in Table 2 as samples, the following static stability test, viscosity measurement, vibration test, and polymerization test were conducted. [Static Stability Test] A sample was placed in a glass container kept at -15°C, and small amounts were sampled over time from the upper and lower layers of the glass container, and the content of organic peroxide was measured by iodometry. The stable period was defined as the number of days until the difference in organic peroxide content between the upper layer and the lower layer became 10% or more. The results are shown in Table 3. [Viscosity measurement] The viscosity of the sample at 0° C. immediately after production was measured using a B-type viscometer (Tokyo Keiki Seisakusho, rotation speed: 30 RPM). Next, at −15°C, _the ratio _{(η 60 /}
η ₆ ) was determined, and this value was used as a measure of thixotropy. [Vibration Test] Approximately 300 g of the sample was vibrated for 5 hours at a temperature of -15° C. using a vibrator (Micromixer MT, Taiyo Kagaku Kogyo Co., Ltd.), and then the viscosity was measured. Furthermore, one month after production, the viscosity was measured immediately after and after production. The results are shown in Table 3.

【table】

[Table] Table 3 shows that the examples have better standing stability than the comparative examples, and are also more stable against vibration.
The viscosity is low at low temperatures and does not thicken over time. Furthermore, the viscosity ratio is close to 1, indicating excellent initial fluidity. [Polymerization Test] Polymerization tests of vinyl chloride were conducted as follows using the aqueous emulsified organic peroxides of the present invention shown in Examples 1 to 10 as polymerization initiators. That is, 0.45 parts by weight of polyvinyl alcohol, 300 parts by weight of water of vinyl chloride, and the amount of aqueous emulsified organic peroxide shown in Table 4 were placed in an autoclave and heated with stirring until the temperature reached 58°C. The reaction was continued until the polymerization reaction was completed. The resulting polymer was filtered and dried to obtain white powder and polyvinyl chloride. The yield is shown in Table 4.

【table】

[Table] Table 4 shows that polyvinyl chloride can be synthesized in high yield by carrying out a polymerization reaction using the polymerization initiator according to the present invention.

Claims (1)

[Scope of Claims] 1 Composed of fatty acid esters of sorbitol, sorbitan, and sorbite having 10 to 22 carbon atoms, and the content of sorbitol fatty acid ester, sorbitan fatty acid ester, and sorbite fatty acid ester is 30% or less and 40% by weight, respectively. Below, a nonionic surfactant mixture whose hydroxyl value is 50% or less and whose hydroxyl value is 60 to 230, a saponification degree of 50 to 95 mol%,
Average degree of polymerization is 10-600, block character is
An aqueous emulsion organic peroxide containing partially saponified polyvinyl acetate having a concentration of 0.7 or less, an organic peroxide, and a freezing point depressant as substantial main components. 2 The content of the nonionic surfactant mixture is 0.1
~10% by weight, the content of partially saponified polyvinyl acetate is
0.1-10% by weight, organic peroxide content 5-80
The aqueous emulsified organic peroxide according to claim 1, wherein the content of the freezing point depressant is 2 to 30% by weight. 3. A polymerization initiator for suspension polymerization or copolymerization of ethylenically unsaturated monomers comprising the aqueous emulsified organic peroxide of claim 1.