JPH07316232A - Production of vinylidene chloride copolymer powder - Google Patents

Abstract

PURPOSE:To obtain a method for producing a vinylidene chloride copolymer powder which does not solidify during storage or drying and has excellent barrier properties by flocculating a water-base dispersion obtd. by emulsion polymn. and heating the resulting flocculate to enhance the crystallinity. CONSTITUTION:A water-base dispersion of a vinylidene chloride copolymer obtd. by emulsion polymn. of 88-93wt.% vinylidene chloride and 12-7wt.% at least one monomer copolymerizable therewith is flocculated, thermally treated at 60-90 deg.C for 30min to 6hr, dried, and powdered. The flocculation is done by adding the dispersion dropwise to or ejecting it into an aq. soln. of a flocculant, by adding the dispersion dropwise to or ejecting it into a poor solvent, or by stirring the dispersion at a high speed. Acrylonitrile is esp. pref. as the monomer copolymerizable with vinylidene chloride.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinylidene chloride copolymer powder having excellent barrier properties in which the powder particles do not solidify during storage or drying.

[0002]

2. Description of the Related Art A coating film obtained from a vinylidene chloride-based copolymer is characterized by excellent barrier properties. Therefore, when coated on a plastic film or the like and used as a packaging material for food, it blocks oxygen and water vapor, and the packaged food can be stored for a long time without getting wet or oxidized. Some plastic films have excellent barrier properties against oxygen or water vapor,
Except for vinylidene chloride-based copolymers, those capable of blocking both oxygen and water vapor at a high level are rare. Therefore, a plastic film coated with a vinylidene chloride copolymer is widely used mainly as a food packaging material.

As a vinylidene chloride-based copolymer for coating, there is an aqueous dispersion obtained by emulsion polymerization, but a water-soluble substance such as a surfactant used at the time of polymerization remains in the coating film. When sterilized in water, there are problems that the barrier property is lowered and the coating film is whitened. For it,
The powder of vinylidene chloride-based copolymer obtained by aggregating the aqueous dispersion obtained by emulsion polymerization has much less water-soluble substances such as surfactants than the aqueous dispersion, and this powder is used as an organic solvent. When it is dissolved in and is applied to a plastic film or the like, a coating film having an excellent barrier property per unit thickness can be obtained.

As a method for obtaining the powder of the vinylidene chloride copolymer, a method of obtaining a powder by aggregating an aqueous dispersion obtained by emulsion polymerization is generally used. Further, for example, many methods have been proposed in which an aqueous dispersion is added to a coagulating liquid such as an acid or a polyvalent inorganic salt solution to coagulate a polymer to obtain a powder from the aqueous dispersion. For example, JP-A-56-106
Japanese Patent Laid-Open No. 925 and Japanese Patent Application Laid-Open No. 60-127312 propose a method in which an acrylic latex and an SB latex are added to a heated coagulant to cause aggregation. It is possible to obtain a powder by coagulating a vinylidene chloride-based copolymer in the same manner, but when dried at a high temperature, it easily solidifies in a line or a drying furnace, and the powder is stored during storage at high temperatures in summer. There was a problem that they would harden each other.
Therefore, when the polymer is dried, it is necessary to dry it at a low temperature for a long time, and since it has to be stored at a temperature as low as possible, a great cost is required during production, storage and transportation.

[0005]

DISCLOSURE OF THE INVENTION The object of the present invention is to cause a problem that powders are hardened and adhered to a vessel wall during drying at a high temperature or a problem that powders are hardened when stored in a high temperature warehouse in summer. Another object of the present invention is to provide a method for producing a vinylidene chloride-based copolymer powder having a high barrier property.

[0006]

Means for Solving the Problems As a result of intensive studies on the above-mentioned problems, it was found that the problems can be achieved by heating for a long time at the time of aggregation to enhance the crystallinity, and the present invention was completed. That is, the present invention relates to vinylidene chloride 88-
After 93% by weight and emulsion polymerization of 12 to 7% by weight of one or more kinds of monomers copolymerizable with vinylidene chloride, the resulting aqueous dispersion of vinylidene chloride copolymer is aggregated, After heat treatment at 60 to 90 ° C. for 30 minutes to 6 hours,
A method for producing a vinylidene chloride-based copolymer powder, which comprises drying and powdering.

In the present invention, if the heating temperature is lower than 60 ° C., the powders are likely to harden after drying. Also, 90 ℃
If it exceeds, the powder is significantly discolored. Further, if the heating time is shorter than 30 minutes, the effect of suppressing the solidification of the powder is small, which is not preferable. Further, if the heating time exceeds 6 hours, the powder is discolored and the productivity is lowered, which is not preferable. Also, the preferable range of the heating time depends on the heating temperature,
When the temperature is high, the effect can be seen in a short time, but conversely, when it is heated for a long time, the color tends to change. Therefore, the heating conditions are generally such that the temperature is 60 to 90 ° C. and the time is 30 minutes to 6 hours, preferably 65 to 85 ° C. and 30 minutes to 4 hours.
The time is more preferably 70 to 80 ° C. and 50 minutes to 2 hours. Further, when the content of vinylidene chloride is less than 88% by weight, sufficient barrier properties cannot be obtained, and the effect of suppressing solidification of the powder is small, which is not preferable. When it exceeds 93% by weight, the solubility of the powder in a solvent becomes poor, which is not preferable. Therefore, the content of vinylidene chloride needs to be in the range of 88 to 93% by weight.
More preferably, it is within the range of 9 to 92% by weight.

Specific examples of the monomer copolymerizable with vinylidene chloride used in the present invention include acrylic acid esters such as methyl acrylate and butyl acrylate, methacrylic acid esters such as methyl methacrylate, acrylonitrile and methacrylic acid. Ronitrile and unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, etc. 1
One kind or two or more kinds can be selected and used. Of these, acrylonitrile is particularly preferable.

Further, as a method for agglomerating the vinylidene chloride copolymer, for example, the following method can be mentioned. Further, a method in which the following methods are combined is also preferable. 1) A method of aggregating a polymer in an aqueous dispersion by dropping an aqueous dispersion of a vinylidene chloride copolymer into an aqueous solution of a coagulant or by ejecting the aqueous dispersion from a nozzle. 2) A method in which an aqueous dispersion of a vinylidene chloride copolymer is dropped in a poor solvent such as methanol or toluene, or is jetted into the liquid from a nozzle to cause aggregation.

3) A method in which an aqueous dispersion of a vinylidene chloride-based copolymer is agitated at high speed to cause aggregation. Specific examples of the coagulant used in the above method, for example, acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, phosphoric acid or alkali metal salts such as sodium chloride, calcium chloride, alkaline earth metal salts such as magnesium sulfate, Aluminum metal salts such as aluminum sulfate may be used, and these may be used alone or in combination. The addition amount is not particularly limited, but is usually about 0.05 to 10% by weight with respect to the polymer content of the water dispersion, and the smaller the addition amount is, the more the amount contained in the powder can be reduced, which is preferable.

After the vinylidene chloride copolymer is agglomerated by the above method, it is heat treated at 60 to 90 ° C., and then the polymer is thoroughly washed and dried to remove the water content in the polymer. A vinylidene-based copolymer powder is obtained. At this time, if the washing is insufficient, a large amount of inorganic salts and surfactants remain in the polymer, which adversely affects the physical properties of the coating film. Therefore, washing should be performed with as clean water as possible to leave no water-soluble substance in the polymer. It is desirable to keep in mind such a cleaning method. For the purpose of the present invention, it is preferable to carry out the drying at a high temperature.
Drying is performed at ˜90 ° C., more preferably 50˜80 ° C.

[0012]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the examples. Further, in the examples, simply referred to as parts or% means parts by weight or% by weight. The physical properties of the product were evaluated by the following methods. Polymer coagulability A coagulated slurry obtained by aggregating an aqueous dispersion of vinylidene chloride copolymer is filtered through a 400-mesh wire net, and then 10 g of the powder remaining on the wire net is put in a glass test tube, and 20 g on top of it. Then, the weight was put on the plate and left at 80 ° C. for 30 minutes. After that, the polymer was taken out and the aggregation state was observed. Method for producing lacquer coat film After adding 10 parts of vinylidene chloride copolymer powder to 100 parts of methyl ethyl ketone, the mixture was stirred at 70 ° C for 30 minutes. The lacquer thus obtained was coated on a biaxially oriented polypropylene film (thickness 20 μm) in a dry coating amount of 3 g /
It was coated so as to have a surface area of m ² and dried in an oven maintained at 120 ° C. for 60 seconds. This coated film was aged in an oven kept at 40 ° C. for 2 days, and then the following measurements were carried out.

Regarding the coated film obtained by the oxygen transmission rate, JIS K 7
According to 126 B method (isobaric method), OXTRAN-100
20 (manufactured by Modern Control)
Oxygen permeability was measured under the condition of 70 ° C and a relative humidity of 70% RH, and the measured value was converted to a coating amount of 3 g / m ² . Transparency of the coating film The transparency when four coat films obtained were stacked was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd.).

[0014]

Example 1 100 parts of ion-exchanged water, 0.06 part of sodium alkylsulfate and 0.9 part of sodium persulfate were charged in a pressure-resistant reactor provided with a glass lining, and after degassing, the temperature of the contents was adjusted. It was kept at 50 ° C. 91% by weight of vinylidene chloride and 9% by weight of acrylonitrile were weighed and mixed in another container to prepare a monomer mixture. After 0.5 part of acrylonitrile and 0.5 part of acrylic acid were added to the reactor, 3 parts of the above-mentioned monomer mixture was charged, and immediately after that, 97 parts of the remaining monomer mixture was continuously added over 16 hours. At this time, sodium bisulfite 0.1
Parts were also added continuously with the monomer. After the total amount of the monomer mixture was added, the internal pressure immediately began to drop, and the reaction was allowed to proceed until the internal pressure was no longer reduced to obtain an aqueous dispersion of vinylidene chloride copolymer A. 30 g of the thus-obtained vinylidene chloride-based aqueous dispersion was dropped into 100 g of a 3% aqueous solution of calcium chloride heated to 60 ° C. while stirring, and then the temperature was raised to 70 ° C. and the mixture was allowed to stand for 2 hours with stirring. The aggregate was washed with water and dried at 60 ° C to obtain a white powder. Table 1 shows the results of evaluation of coating film physical properties of the thus-obtained vinylidene chloride-based copolymer powder and the precursor polymer by the above-described methods, together with the following Examples and Comparative Examples.

[0015]

Example 2 30 g of an aqueous dispersion of the vinylidene chloride copolymer A obtained in Example 1 was added dropwise to 100 g of a 1% aluminum sulfate aqueous solution heated to 60 ° C. with stirring, and then the temperature was raised to 80 ° C. After the temperature was raised and the mixture was allowed to stand for 1 hour with stirring, the formed aggregate was washed with water and dried at 60 ° C. to obtain a white powder.

[0016]

Example 3 To 30 g of the aqueous dispersion of vinylidene chloride copolymer A obtained in Example 1, 100 g of a 2% calcium chloride aqueous solution was added dropwise with stirring, and then the mixture was stirred with a homogenizer at 15000 rpm for 30 minutes. After agglomerating, the temperature was raised to 80 ° C. and left for 2 hours, then the agglomerates formed were washed with water and dried at 60 ° C. to obtain a white powder.

[0017]

Example 4 100 parts of ion-exchanged water, 0.1 part of sodium alkylsulfate and 0.9 part of sodium persulfate were charged in a pressure-resistant reactor having a glass lining, and after degassing, the temperature of the contents was adjusted. It was kept at 50 ° C. 91% by weight of vinylidene chloride and 9% by weight of acrylonitrile were weighed and mixed in another container to prepare a monomer mixture. After 0.5 part of acrylonitrile and 0.8 part of acrylic acid were added to the reactor, 5 parts of the above-mentioned monomer mixture was charged, and immediately after that, 95 parts of the remaining monomer mixture was continuously added over 16 hours. At this time, 0.1 part of sodium hydrogen sulfite was also continuously added together with the monomer. After the total amount of the monomer mixture was added, the internal pressure began to drop immediately, and the reaction was allowed to proceed until the internal pressure was no longer reduced to obtain an aqueous dispersion of vinylidene chloride copolymer B. 30 g of the thus-obtained vinylidene chloride-based aqueous dispersion was dropped into 500 g of methanol to which 1 g of concentrated hydrochloric acid had been added with stirring, and then filtered through a wire mesh to obtain a powder of an aggregate. This powder was added to 500 g of water, the temperature was raised to 80 ° C., and the mixture was allowed to stand for 1 hour with stirring. After that, the powder of the agglomerates formed was washed with water and dried at 60 ° C. to obtain a white powder.

[0018]

Example 5 100 parts of ion-exchanged water, 0.1 part of sodium alkylsulfate and 0.9 part of sodium persulfate were charged in a pressure-resistant reactor provided with a glass lining, and after degassing, the temperature of the contents was adjusted. It was kept at 50 ° C. 92.5% by weight of vinylidene chloride and 7.5% by weight of acrylonitrile were weighed and mixed in another container to prepare a monomer mixture. 0.5 parts of acrylonitrile and 0.
After adding 5 parts, 4 parts of the above-mentioned monomer mixture was charged, and immediately after that, 96 parts of the remaining monomer mixture was continuously added over 16 hours. At this time, 0.1 part of sodium hydrogen sulfite was also continuously added together with the monomer. After the total amount of the monomer mixture was added, the internal pressure began to drop immediately, and the reaction was allowed to proceed until the internal pressure was no longer reduced to obtain an aqueous dispersion of vinylidene chloride copolymer C. 30 g of the thus obtained aqueous dispersion was added dropwise to 100 g of a 3% aqueous solution of calcium chloride heated to 60 ° C. with stirring,
After the temperature was raised to 80 ° C. and the mixture was left for 2 hours with stirring, the generated aggregate was washed with water and dried at 60 ° C. to obtain a white powder.

[0019]

Example 6 100 parts of ion-exchanged water, 0.1 part of sodium alkylsulfate and 0.9 part of sodium persulfate were charged in a pressure resistant reactor provided with a glass lining, and after degassing, the temperature of the contents was adjusted. It was kept at 50 ° C. In another container, 92% by weight of vinylidene chloride and 8% by weight of acrylonitrile were measured and mixed to prepare a monomer mixture. After 1 part of acrylonitrile and 0.5 part of itaconic acid were added to the reactor, 3 parts of the above-mentioned monomer mixture was charged, and immediately after that, 97 parts of the remaining monomer mixture was continuously added over 16 hours. At this time, 0.1 part of sodium hydrogen sulfite was also continuously added together with the monomer. After the total amount of the monomer mixture was added, the internal pressure began to drop immediately, and the reaction was allowed to proceed until the internal pressure was no longer reduced to obtain an aqueous dispersion of vinylidene chloride copolymer D. 30 g of the aqueous dispersion thus obtained
100% 1% aluminum sulfate aqueous solution heated to 60 ° C
After adding dropwise to the solution with stirring, the temperature was raised to 70 ° C. and left for 2 hours with stirring.

[0020]

Comparative Example 1 30 g of an aqueous dispersion of the vinylidene chloride-based copolymer A obtained in Example 1 was dropped into 500 g of methanol containing 1 g of concentrated hydrochloric acid with stirring, and then filtered through a wire mesh to form an aggregate. Of powder was obtained. This powder was washed with water and dried at 40 ° C to obtain a white powder.

[0021]

Comparative Example 2 30 g of an aqueous dispersion of the vinylidene chloride copolymer A obtained in Example 1 was added dropwise to 100 g of a 2% calcium chloride aqueous solution heated to 60 ° C. with stirring, and then the temperature was raised to 70 ° C. It was put in warm hot water, heated for 5 minutes, washed with water and dried at 40 ° C. to obtain a white powder.

[0022]

[Comparative Example 3] 100 parts of ion-exchanged water, 0.06 part of sodium alkylsulfate and 0.9 part of sodium persulfate were charged in a pressure-resistant reactor provided with a glass lining, and after degassing, the temperature of the contents was adjusted. It was kept at 50 ° C. 86% by weight of vinylidene chloride and 13% by weight of acrylonitrile in another container
Were measured and mixed to prepare a monomer mixture. After 0.5 part of acrylonitrile and 0.5 part of acrylic acid were added to the reactor, 3 parts of the above-mentioned monomer mixture was charged, and immediately after that, 97 parts of the remaining monomer mixture was continuously added over 16 hours. At this time, sodium bisulfite 0.
One part was also added continuously with the monomer. After the total amount of the monomer mixture was added, the internal pressure began to drop immediately, and the reaction was allowed to proceed until the internal pressure was no longer reduced to obtain an aqueous dispersion of vinylidene chloride copolymer E. 30 g of the thus-obtained aqueous dispersion was added dropwise to 100 g of a 3% aqueous solution of calcium chloride heated to 60 ° C. with stirring, the temperature was raised to 80 ° C., and the mixture was left for 2 hours with stirring. Was washed with water and dried at 40 ° C. to obtain a white powder.

As is clear from Examples 1 to 6 in Table 1,
According to the present invention, no cohesion is observed even when dried at 80 ° C., and the coating film exhibits excellent transparency and barrier properties. On the other hand, in Comparative Examples 1, 2, and 3, when the polymer was heated at 80 ° C., it was completely aggregated into a lump.

[0024]

[Table 1]

[0025]

EFFECTS OF THE INVENTION According to the production method of the present invention, the trouble of powder solidifying during drying and storage does not occur. Therefore, the productivity is improved, and the low temperature control during transportation and storage is not necessary, so that the cost can be significantly reduced.

Claims (1)

[Claims] 1. 88 to 93% by weight of vinylidene chloride and at least one monomer 12 copolymerizable with the vinylidene chloride.
~ 7 wt% by emulsion polymerization, after aggregating the resulting aqueous dispersion of vinylidene chloride copolymer, after heat treatment at 60 ~ 90 ℃ for 30 minutes ~ 6 hours, dried, powder A method for producing a vinylidene chloride-based copolymer powder, comprising: