JP2000239468A - Low-foaming vinylidene chloride-based latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain low foamability by incorporating an antifoaming agent comprising a mineral oil and a surfactant at a specific ratio into a resin component of a vinylidene chloride-based copolymer latex obtained by emulsion polymerization of vinylidene chloride and at least one monomer copolymerizable therewith each in a specific amount. SOLUTION: Into 100 pts.wt. of a resin component of a vinylidene chloride- based copolymer latex obtained by emulsion polymerization of 50-94 wt.% of vinylidene chloride and 50-6 wt.% of at least one monomer copolymerizable therewith is incorporated 0.005-0.1 pt.wt. of an antifoaming agent comprising 20-50 wt.% of a mineral oil and 80-50 wt.% of a surfactant. The mineral oil is not particularly limited and there can be exemplified paraffinic mineral oils, naphthenic mineral oils and the like. Nonionic, anionic, cationic and amphoteric surfactants can be arbitrarily used as the surfactant, and an anionic or nonionic surfactant suitable for the preparation of a vinylidene chloride-based latex is desirably employed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vinylidene chloride-based latex for film coating having a low foaming amount.

[0002]

2. Description of the Related Art A plastic film coated with a vinylidene chloride-based latex has an excellent barrier property, and is mainly used as a food packaging material by blocking oxygen and water vapor to prevent the packaged food from becoming wet or oxidized. It is used to allow long-term storage. Some of the plastic films have excellent barrier properties against oxygen or water vapor, but those which can block both oxygen and water vapor at a high level are rare except for vinylidene chloride copolymers. For this reason, films coated with a vinylidene chloride-based copolymer are widely used mainly as food packaging materials.

[0003] Since this vinylidene chloride-based latex is produced by an emulsion polymerization method, a surfactant is always contained in the latex. There are four types of surfactants: nonionic, anionic, cationic and amphoteric. In the production of vinylidene chloride-based latex, anionic and nonionic surfactants are mainly used. The surfactant is
It has a role as a dispersion stabilizer for stably dispersing the polymer particles in the latex, and a role as a coating improver for allowing the latex to be applied neatly without repelling on the plastic film. Therefore, the vinylidene chloride-based latex contains several percent of a surfactant.

[0004] In addition to the above-mentioned advantages, the surfactant has a characteristic that foam is easily formed. When applying vinylidene chloride-based latex onto a plastic film, if the latex foam is applied, the foam is dried while the foam is transferred to the coated surface, and crater-like foam marks are left on the dried coated surface. The problem that remains remains. If such traces remain on the coated surface, they become defective portions such as ink jumps during printing, and impair the appearance of the product. Therefore, there is a demand for latex foam which cannot be produced as much as possible or which can be broken and disappear within a short period of time.

Examples of adding a defoaming agent to a vinylidene chloride-based latex can be found in JP-A-62-565 and JP-A-5-140501, all of which are examples of vinylidene chloride-based latex for paints. In addition, a large amount of about 1% of an antifoaming agent is added to the resin component of the vinylidene chloride-based latex. When a large amount of an antifoaming agent is added for a plastic film, the defoaming effect is excellent, but latex repels at the time of coating, so that a uniform coating film cannot be obtained.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vinylidene chloride-based latex for film coating, which has less foaming property than the prior art.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a vinylidene chloride-based latex containing a trace amount of a specific antifoaming agent has excellent coatability on a plastic film, In addition, they have found that foaming of latex can be suppressed, and have completed the present invention. That is, the present invention provides: A resin component of a vinylidene chloride copolymer latex obtained by emulsion polymerization of 50 to 94% by weight of vinylidene chloride and 50 to 6% by weight of at least one monomer copolymerizable with vinylidene chloride. Low foaming vinylidene chloride latex for film coating, containing 0.005 to 0.1 parts by weight of an antifoaming agent composed of 20 to 50% by weight of a mineral oil and 80 to 50% by weight of a surfactant with respect to 100 parts by weight. I will provide a. It is also characterized in that the surfactant contained in the defoaming agent is at least one selected from nonionic and anionic surfactants. The present invention also provides a method for producing a vinylidene chloride-based latex-coated film, which is applied on a plastic film or after applying the described vinylidene chloride-based latex at ² to 10 g / m ² and then dried.

Hereinafter, the present invention will be described in detail. (i) Film to be coatedHere, the plastic film for coating the vinylidene chloride-based latex according to the present invention is not particularly limited, for example, polyester, polyamide, polyimide,
Examples include polypropylene, polyethylene, polyvinyl alcohol, cellophane, polystyrene, polyvinyl chloride, ethylene-vinyl alcohol copolymer, and polycarbonate.

(Ii) Vinylidene chloride-based latex Composition of vinylidene chloride-based copolymer The vinylidene chloride-based copolymer constituting the vinylidene chloride-based latex used in the present invention is vinylidene chloride 5
It must be composed of 0 to 94% by weight and 50 to 6% by weight of one or more monomers copolymerizable with vinylidene chloride. If the ratio of vinylidene chloride in this copolymer exceeds 94% by weight, the film-forming properties become poor, which is not preferable for practical use. On the other hand, if it is less than 50% by weight, the barrier properties are poor, which is not practically preferable. Therefore, the vinylidene chloride content of the copolymer needs to be in the range of 50 to 94% by weight, and more preferably in the range of 80 to 92% by weight.

Specific examples of monomers copolymerizable with vinylidene chloride include vinyl chloride; acrylic acid such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate. Esters; methyl methacrylate,
Methacrylic acid esters such as glycidyl methacrylate; unsaturated nitriles such as acrylonitrile and methacrylonitrile; and one or more selected from unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid and maleic acid. Can be used.

Specific Antifoaming Agent 1) In the present invention, a specific composite antifoaming agent is added in a trace amount to 100 parts by weight of the resin component of the vinylidene chloride-based latex.
That is, 20 to 50% by weight of mineral oil and 80 to 50 of surfactant
It is necessary to contain 0.005 to 0.1 parts by weight, preferably 0.01 to 0.08% by weight of an antifoaming agent composed by weight. 2) Surfactant As the surfactant constituting the composite antifoaming agent of the present invention, nonionic, anionic, cationic and amphoteric surfactants can be used arbitrarily, but they are used for the production of vinylidene chloride-based latex. The use of suitable anionic or nonionic surfactants is desirable. Among them, the nonionic surfactants include, for example, polyethylene glycol type nonionic surfactants obtained by reacting fatty acid alcohols, alkylphenols, fatty acids, fatty acid amides and the like with ethylene oxide, or polyhydric alcohols such as glycerin and sorbitan and fatty acids. It is preferable to use one or more kinds of polyhydric alcohol type nonionic surfactants reacted with the above. Further, as the anionic surfactant, for example, one or more kinds of fatty acid salts, sulfate salts, sulfonates, phosphate salts and the like having an alkyl group or an alkylphenyl group are preferably used.

3) Mineral oil The mineral oil is not particularly limited, and examples thereof include a paraffinic mineral oil and a naphthenic mineral oil. 4) Amount of surfactant When the amount of the surfactant in the defoaming agent is less than 50% by weight and less than the amount of the mineral oil, when the vinylidene chloride-based latex to which the antifoaming agent is added is applied to the film. Is easy to repel, which is not preferable. In addition, the amount of the surfactant is 4
If the ratio is more than twice, the defoaming property of the vinylidene chloride-based latex is impaired, which is not preferable. Therefore, the ratio of mineral oil / surfactant in the antifoaming agent is preferably 2/8 to 5/5, and 3 /
It is more preferable that it is within the range of 7 to 4/6. 5) Other additives In addition to the mineral oil and the surfactant, a small amount of hydrophobic silica, amide, water or the like may be added to the defoaming agent. The amount of the other additives is preferably 10% or less based on the total amount of the mineral oil and the surfactant.

6) Addition amount of composite antifoaming agent In the present invention, 0.1 parts by weight of the composite antifoaming agent is added to 100 parts by weight of the resin component of the vinylidene chloride-based copolymer latex.
005 to 0.1 parts by weight. The conventional vinylidene chloride copolymer latex is mainly used for metal coating, and as is apparent from the description of the above-mentioned "prior art", Japanese Patent Application Laid-Open Nos. -1
According to Japanese Patent No. 40501, at present, a large amount of about 1% of an antifoaming agent is added to a resin component of a vinylidene chloride-based latex. In contrast, in the vinylidene chloride latex for film coating of the present invention,
0.005 to 0.005
Since only a very small amount of 0.1 parts by weight can be used, there is an advantage that a uniform coating film can be obtained without repelling when coating on a film. That is, if the added amount of the composite antifoaming agent is less than 0.005 part by weight, the defoaming effect of the latex is unfavorably deteriorated, and if it exceeds 0.1 part by weight, repelling tends to occur, which is not preferable. More preferably, the added amount of the composite antifoaming agent is 0.01 to 0.08 parts by weight.

Coating amount of vinylidene chloride-based latex When coating vinylidene chloride-based latex on a film, the coating amount of the latex is large, so that the film is easily repelled. Therefore, the coating amount of the vinylidene chloride-based latex is 2 to 10
It is preferably within the range of g / m ² . A reverse gravure coater is most preferable as an apparatus for applying such a low coating amount.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples. Also, in the examples, parts or% are simply
It means parts by weight or% by weight. In addition, physical property evaluation was calculated | required by the following method. (1) Coatability The latex is coated on a corona-treated surface of an OPP film (thickness: 20 μm) so as to have a coating amount of 10 g / m ² and dried with a hot air drier at 100 ° C. for 30 seconds. Was visually observed, and the following judgment was made. ：: No repelling was observed on the coated surface. Δ: Less than 10 repelling was observed on a 10 cm square coated surface. X: 10 or more cissing was observed in a 10 cm square coating surface. (2) Foaming property of latex Air was blown into the latex placed in a 45 mm diameter glass tube at a rate of 100 ml / min for 5 minutes at a rate of 100 ml / min in a 25 ° C. atmosphere, and the foam remaining after standing for 5 minutes The following judgment was made from the height of the sample. ：: height of remaining foam is less than 5 cm △: height of remaining foam is 5 to 10 cm ×: height of remaining foam is 10 cm or more

(Example 1) Glass-lined resistant
In a pressure reactor, 100 parts of ion-exchanged water, alkyl sulfo
Sodium acid salt (Katesha, product name "Latemul PS")
Degas by charging 0.2 parts and 0.2 parts of sodium persulfate
After that, the temperature of the contents was kept at 50 ° C. Chloride in another container
90% by weight of vinylidene, 9.5% by weight of methyl acrylate
% And acrylic acid 0.5% by weight.
A compound was created. The above monomer mixture in the reactor
After adding 10 parts, the internal pressure of the polymerization machine is 0.2 kg higher than the maximum pressure.
/ Cm ^TwoWhen lowered, 90 parts by weight of the remaining monomer mixture
And 0.7 parts of sodium alkylsulfonate
did. Then the internal pressure is 0.8kg / cm^TwoUntil lower
After proceeding with the reaction, heat to 60 ° C and
Nomer was removed. Alkylsulfo in this latex
The surface tension at 20 ° C is 40m
It was adjusted to be N / m.

In this latex, an antifoaming agent composed of 40% of mineral oil (manufactured by Wako Pure Chemical Industries) and 60% of a nonionic surfactant (manufactured by Kao Corporation, trade name: Emulgen 404) is mixed with a latex resin. 0.03 for 100 parts by weight
An amount by weight was added and stirred for 30 minutes. The vinylidene chloride-based latex thus obtained was evaluated. (Examples 2-3) The addition amount of the defoamer of Example 1 was set to 0.08.
The vinylidene chloride-based latex prepared in the same manner as in Example 1 except that the amount was changed to 0.008 parts by weight was evaluated.

Comparative Example 1 A vinylidene chloride-based latex prepared in the same manner as in Example 1 except that the defoaming agent of Example 1 was not added at all was evaluated. Comparative Example 2 The vinylidene chloride-based latex prepared by adding 0.2 parts by weight of the defoamer of Example 1 to the vinylidene chloride-based latex of Example 1 was evaluated.

(Examples 4 and 5) Vinylidene chloride prepared in the same manner as in Example 1 except that the ratio of mineral oil / nonionic surfactant in the antifoaming agent was 2/8 and 5/5. The latex was evaluated. (Example 6) 40% mineral oil (manufactured by Wako Pure Chemical Industries, Ltd.) and a nonionic surfactant (manufactured by Kao Corporation, trade name: Emulgen 40) were added to the vinylidene chloride-based latex of Example 1.
4) About latex prepared by adding 0.03 part by weight of an antifoaming agent consisting of 30% and 30% of an anionic surfactant (trade name "Latemul PS" manufactured by Kao Corporation) to 100 parts by weight of latex resin. An evaluation was performed.

(Comparative Examples 3 and 4) Vinylidene chloride prepared in the same manner as in Example 1 except that the ratio of mineral oil / nonionic surfactant in the defoamer was 7/3 and 1/9. The latex was evaluated. Table 1 shows the above evaluation results. As is clear from Table 1, Examples 1 to
While the coating films obtained in 6 are all excellent in defoaming property and coating property, those of Comparative Examples 1 to 4 are inferior in either defoaming property or coating property and are not practically preferable. .

[0021]

[Table 1] The abbreviations in the table are as follows. VDC: vinylidene chloride MA: methyl acrylate AA: acrylic acid

[0022]

The vinylidene chloride-based latex for film coating of the present invention is extremely excellent in defoaming property without impairing the coating property and the physical properties of the coating film with respect to the plastic film. The problem of poor appearance of the painted surface can be solved.

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Claims (3)

[Claims] 1. A resin component 100 of a vinylidene chloride-based copolymer latex obtained by emulsion polymerization of 50 to 94% by weight of vinylidene chloride and 50 to 6% by weight of one or more monomers copolymerizable with vinylidene chloride. Mineral oil 2 to parts by weight
A low-foamable vinylidene chloride latex for film coating, comprising 0.005 to 0.1 parts by weight of an antifoaming agent comprising 0 to 50% by weight and 80 to 50% by weight of a surfactant. 2. The low foaming vinylidene chloride for film coating according to claim 1, wherein the surfactant contained in the defoaming agent comprises at least one selected from nonionic and anionic surfactants. Latex. 3. The vinylidene chloride-based latex according to claim 1 or 2 on a plastic film.
^{2. A} method for producing a vinylidene chloride-based latex coated film, characterized by drying after coating.