JPS6216966B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composition for coating plastics having antistatic properties and comprising an aqueous dispersion of an acrylic copolymer blended with a conductive polymer electrolyte. In recent years, various acrylic copolymer compositions have been proposed that can be applied to plastic films (hereinafter simply referred to as films) using an aqueous medium and can impart heat-sealing properties to the films. (For example, U.S. Patent No. 3753769
No. 24223) The present inventors also invented a coating composition with excellent heat-sealability consisting of an aqueous dispersion containing a specific acrylic copolymer, and previously filed a patent application.
(Japanese Patent Application No. 73498/1982) Since these coating compositions use water as a medium, there is a risk of ignition caused by the solvent and problems of solvent inhalation that occur when using conventional coating compositions that use an organic solvent as a medium. It is known that there is no problem of residual solvent in the coating film, and the films coated with these coating compositions have transparency, light stability, and easy heat sealability, and are excellent as packaging materials. There is. However, since this coating film does not have antistatic properties, it is easy to generate and accumulate static electricity due to contact, peeling, friction, etc. The film attracts each other, resulting in poor automatic feeding, which significantly reduces work efficiency, and also causes dust collection and dirt on the film surface of the product, extremely reducing the product value. In order to eliminate such problems caused by electrostatic charging, it is desired to impart antistatic properties to this coating film. In order to impart heat-sealability and antistatic properties to a film, a method has been adopted in which an antistatic agent is further applied to the surface of the film coated with a resin composition having heat-sealability. However, this method requires at least two coating steps;
It is not economical, and the applied antistatic agent is easily removed by washing with water or rubbing, and the antistatic effect is lost, which is not preferable. On the other hand, as a method for improving these drawbacks, there is a method in which an antistatic agent is blended into a resin composition that imparts heat-sealing properties and applied to the film. However, in this method, it is more difficult to select a combination of an antistatic agent and a resin composition that imparts heat-sealing properties than in the above-described method. The present inventors also carried out such a method using an acrylic copolymer as a resin composition that imparts heat-sealing properties, and a conductive low-molecular surfactant, which is commonly used as an antistatic agent. Attempts were made to impart heat-sealing properties and antistatic properties to the film, but if the film had sufficient heat-sealing strength, it would not be possible to impart high antistatic properties suitable for modern high-speed packaging machines; However, if sufficient antistatic properties are applied, the heat sealing properties will be lost.
It has not been possible to find a combination of an acrylic copolymer and a conductive low-molecular-weight surfactant that can satisfy both heat-sealing properties and antistatic properties. The present inventors have developed an antistatic agent that imparts high antistatic properties without impairing the heat sealing properties of an acrylic copolymer composition that can be applied to a film using an aqueous medium. As a result of further intensive research, we have arrived at the present invention. That is, the present invention comprises (A) (a) 0 to 10% by weight of one or more α,β-unsaturated carboxylic acids and/or salts thereof having one or more carboxyl groups; (b) one or more acrylic acid alkyl esters (the alkyl group of which has 1 to 12 carbon atoms) and/or methacrylic acid alkyl esters (the alkyl group of which has 1 to 12 carbon atoms);
one or more types of (having 12 carbon atoms)
10 to 98% by weight, and if necessary, (c) one or more copolymerizable vinyl monomers 0 to 80% by weight.
% by weight, the copolymer has an average molecular weight of 5,000 to 150,000 and a second-order transition temperature of 20 to 100°C. Solid content of aqueous polymer dispersion
(B) carboxyl group in the molecule, per 100 parts by weight;
A coating composition containing 0.5 to 15 parts by weight of one or more conductive polymer electrolytes containing at least one of a sulfonic acid group, a quaternary ammonium group, and/or a salt thereof. It is a composition for coating plastics which is excellent in that it can impart easy heat-sealability and high antistatic properties to the film, especially when applied to the film. The α,β-unsaturated carboxylic acid having one or more carboxyl groups or its salt used to form the acrylic copolymer of the present invention (a) is, for example, acrylic acid, Methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid,
or its alkali metal salts or ammonium salts. Alternatively, when an α,β-unsaturated carboxylic acid having two or more carboxyl groups or a salt thereof is used, a half ester thereof may be used.
These carboxylic acids or salts thereof have the effect of mainly improving adhesion to the film, and the amount used is preferably in the range of 0 to 10% by weight. If it exceeds 10% by weight, the water resistance, blocking resistance and abrasion resistance of the resulting coating film will deteriorate, which is not preferable. Furthermore, when producing this aqueous acrylic copolymer dispersion using a cationic emulsifier, it is better to avoid using these carboxylic acids or their salts, since they reduce polymerization stability. In addition, (b) acrylic acid alkyl ester and methacrylic acid alkyl ester are examples in which the alkyl group is methyl, ethyl, isopropyl, n-hexyl, 2-
Acrylates and methacrylates such as ethylhexyl and lauryl. These are necessary components that influence the flexibility and blocking resistance of the resulting coating film and the secondary transition temperature of the resulting polymer, and the amount used is from 10 to 98% by weight. Next, the copolymerizable vinyl monomer (c) includes, but is not limited to, the following). Vinyl-substituted aromatic hydrocarbons such as styrene and α-methylstyrene, α,β-unsaturated aliphatic nitriles such as acrylonitrile and methacrylonitrile, organic acid vinyl esters such as vinyl acetate and vinyl propionate, vinyl chloride , vinyl halides such as vinylidene chloride, α,β-unsaturated carboxylic acid amides such as acrylamide, methacrylamide, and N-methoxyacrylamide, α, such as 2-hydroxyethyl acrylate or methacrylate, 2-hydroxypropylacrylate or methacrylate, etc. , hydroxyalkyl esters of β-unsaturated carboxylic acids, α,β-unsaturated carboxylic acid esters with epoxy groups such as glycidyl acrylate or methacrylate, α,β-unsaturated carboxylic acid esters such as dimethylaminoethyl acrylate or methacrylate, diethylaminoethyl acrylate or methacrylate, etc. , aminoalkyl esters of β-unsaturated carboxylic acids, and these copolymerizable vinyl monomers may be used alone or in combination of two or more, if necessary. The amount used is preferably 0 to 80% by weight in the copolymer. These are thought to mainly affect the hardness and secondary transition temperature of the resulting coating film, but the vinyl monomers listed in ) and) improve the adhesion of the coating composition to the film. will be involved. In particular, hydroxyalkyl esters of α,β-unsaturated carboxylic acids (0.1 to 30%) are highly effective.
It is desirable to use 5% to 30% by weight, preferably 5% to 30% by weight. The target copolymer has an average molecular weight of 5000
~150000, preferably 8000-80000, and a secondary transition temperature of 20-100℃, preferably 25-70℃
It is. When the average molecular weight of the copolymer exceeds 150,000, the adhesion to the film decreases, and the viscous flow required to obtain good heat sealing properties disappears, and when it is below 5,000, it loses its properties as a coating film, resulting in insufficient heat sealing. Strength cannot be obtained. Note that the average molecular weight referred to here is a number average molecular weight. Furthermore, when the secondary transition temperature is below 20°C, the coating film becomes sticky and causes blocking. On the other hand, 100
If the temperature is above ℃, the coating becomes hard and its flexibility decreases.
Heat sealability is impaired. Such an aqueous dispersion of an acrylic copolymer can be produced by a known aqueous medium polymerization method, typified by an emulsion polymerization method. Here, the aqueous medium only needs to substantially contain water, and an aqueous organic solvent such as alcohol may be mixed therein. Furthermore, in the present invention, as an antistatic agent,
Conductive polymer electrolytes containing a carboxyl group, a sulfonic acid group, a quaternary ammonium group, or a salt thereof in the molecule are used, but these conductive polymer electrolytes are monomers containing a carboxyl group or a salt thereof. , for example acrylic acid, maleic acid or
Monomers having these alkali metal salts, ammonium salts, sulfonic acid groups or salts thereof, for example,
Styrene sulfonic acid, sulfopropyl methacrylate, or their alkali metal salts or ammonium salts, as well as quaternary ammonium groups or
Homopolymerization or copolymerization with other monomers as necessary by a known polymerization method using a monomer having a salt thereof, such as vinylbenzyltrimethylammonium chloride, 2-hydroxy-3-methacryloxypropyltrimethylammonium chloride, etc. or a polymer compound in which a carboxyl group, a sulfonic acid group, a quaternary ammonium group, or a salt thereof is later introduced into, for example, polystyrene, the average molecular weight of which is 1,000 to 1,000.
400,000. Many of these conductive polymer electrolytes are commercially available, such as Elecondo PQ (Soken Kagaku Co., Ltd.), which contains at least one of a carboxyl group, a sulfonic acid group, or a salt thereof in the molecule, and Oligo Z. (Tomoekawa Paper Mills Co., Ltd.), ER-
PSV (Mitsubishi Chemical Industries, Ltd.), NAJROL and VERSA
JL (National Starch and Chemical Company), ECR-34 containing a quaternary ammonium group or its salt in the molecule (Dow Chemical Company), Polyamine Sulfone-A (Nitto Boseki Co., Ltd.), Conductive Polymer 261 (Calgon), etc., and these commercially available products can be used as they are. The amount of the conductive polymer electrolyte added to the aqueous acrylic copolymer dispersion is 0.5 to 15 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of solid content in the acrylic copolymer dispersion. Department. If the amount is less than 0.5 parts by weight, the desired antistatic effect cannot be obtained, and if it is more than 15 parts by weight, the conductive polymer electrolyte will have an adverse effect on heat sealing properties and anti-blocking properties, which is not preferable. Further, only one type of conductive polymer electrolyte may be blended, but two or more types can also be used in combination. Methods for blending the conductive polymer electrolyte into the aqueous acrylic copolymer dispersion include adding the conductive polymer electrolyte to the reaction system before the start of polymerization of the copolymer, adding it during the polymerization, or Any method of adding after polymerization can be used.
However, in this case, care must be taken to ensure that the conductive polymer electrolyte does not cause aggregation, gelation, etc. of the aqueous acrylic copolymer dispersion, thereby reducing dispersion stability. From the viewpoint of dispersion stability, an anionic conductive polymer electrolyte containing a carboxyl group, a sulfonic acid group, or a salt thereof in the molecule is used in an anionic acrylic copolymer aqueous dispersion. It is preferable to combine a cationic conductive polymer electrolyte containing a quaternary ammonium group or a salt thereof in the molecule with the combined aqueous dispersion. In addition, a lubricant, an antiblocking agent, a plasticizer, an antifogging agent, a stabilizer, etc. may be added to the plastic coating composition as required. The composition for coating plastics of the present invention can be used not only for plastic films, but also for coating materials such as plastic moldings, paper, metal foils such as aluminum, etc.
Although it can be used as a treatment agent for cloth and fibers, it is particularly effective for use as a coating agent that imparts easy heat-sealing properties and high antistatic properties to plastic films. The target films include, for example, polyolefin films such as polyethylene film, polypropylene film, and polybutene film, polystyrene film, polyamide film, and polyester film. These may be non-stretched, uniaxially stretched or biaxially stretched. However, the plastic coating compositions of the present invention are particularly effective on biaxially oriented polypropylene films. In addition, it is preferable that the contact angle of the film surface to water is 85° or less, and polyamide films and polyester films can be used as they are, but
It is desirable to activate the surface of polystyrene film and polyolefin film by corona discharge treatment, oxidizing agent treatment, etc. before use. Various methods can be used to apply the plastic coating composition of the present invention to a film. For example, a method can be used in which the coating is applied using a coating device such as a roll coater, dip coater, or gravure coater, and then dried. The thickness of the coating film is expressed as solid content per ^1m2 of film surface.
It is sufficient to adjust the amount to about 0.3 to 5 g. Such films can be wrapped as is or made into bags and used for all kinds of packaging.
It is particularly suitable for packaging materials for the outer packaging of cigarettes, caramels, etc., which are packaged using high-speed overlapping automatic packaging machines. The detailed content of the present invention will be explained below using examples. In the same example, all "parts" are "parts by weight." In addition,
In order to evaluate the properties of the coated film, charging characteristics and heat seal strength were measured by the following methods. Charging characteristics: Using a static honest meter (manufactured by Shishido Shokai), 10 KV was applied, and charging voltage and decay half-life time (half-life) were measured at 20° C. and 65% RH. Heat sealing strength: The heater temperature is 90°C, 100°C and 110°C using a bar type heat sealer, combining the film coated side and the coated side.
℃, crimping pressure 1.0Kg/cm ² , crimping time 1
Obtained by heat sealing under conditions of seconds.
The force required to peel a 15 mm x 100 mm sample was measured using a tensile tester at a peel rate of 100 mm/min and a peel angle of 180°. In addition, the monomers used are indicated by the following abbreviations. AA; BA acrylate; n-butyl acrylate DEAEMA; 2-diethylaminoethyl methacrylate EA; Ethyl acrylate HEMA; 2-hydroxyethyl methacrylate HPMA; 2-hydroxypropyl methacrylate MAA; MMA methacrylate; Methyl methacrylate St ;Styrene Example 1 795 parts of water containing 13 parts of sodium dodecylbenzenesulfonate as an emulsifier was charged into a polymerization vessel equipped with a stirrer, a cooler, and a thermometer, and 90 parts of water was added while stirring.
The following additives were simultaneously added dropwise to the mixture while maintaining the temperature at 90°C over 3 hours. Additives (monomer composition) St...234 parts BA...140 parts HEMA...67.5 parts AA...9 parts (Molecular weight regulator) t-dodecyl mercaptan
4.5 parts Additives (polymerization initiator) Potassium persulfate...2.3 parts Water...117 parts After the dropwise addition was completed, the polymerization container was kept at 90°C for an additional 30 minutes. Next, this aqueous acrylic copolymer dispersion was neutralized with aqueous ammonia, kept at 60°C for 1 hour, and then cooled. The second-order transition temperature of the obtained acrylic copolymer is
The temperature was 27.8°C and the average molecular weight was 19,000. Solid content of this acrylic copolymer aqueous dispersion
6 parts of conductive polymer electrolyte Oligo Z M-1010 (Tomoekawa Paper Manufacturing Co., Ltd.) was added as an antistatic agent to 100 parts in solid content. This aqueous dispersion was diluted with water to give a solids concentration of 20% to obtain a composition for coating plastics. Solid content coating amount is approximately 1.2 g/m ² on a 20μ thick corona discharge treated biaxially oriented polypropylene film.
The coating composition was applied to the coating composition and dried at a temperature of 110° C. for 1 minute to obtain a coated film. Example 2 Elecondo PQ instead of Oligo-Z M1010
A plastic coating composition and a coating film were obtained in the same manner as in Example 1 except that A (Soken Kagaku Co., Ltd.) was used. Comparative Example 1 The aqueous acrylic copolymer dispersion obtained in Example 1 without blending a conductive polymer electrolyte was applied to a biaxially stretched polypropylene film in the same manner as in Example 1 to obtain a coated film. Comparative Examples 2 and 3 Conductive low-molecular surfactant Emar T (Kao Atlas Co., Ltd.) or Electrostripper N was used instead of the conductive polymer electrolyte as an antistatic agent.
Example 1 except that 3 parts of (Kao Atlas Co., Ltd.) were used.
A composition for coating plastics and a coating film were obtained in the same manner as above. Table 1 shows the properties of the coated films obtained in Examples 1-2 and Comparative Examples 1-3. Examples 3 to 6 Various acrylic copolymer aqueous dispersions were obtained in the same manner as in Example 1 except that the monomer composition was changed.
Table 2 shows the monomer composition, secondary transition temperature, and average molecular weight of these acrylic copolymers. These acrylic copolymer aqueous dispersions were mixed with various conductive polymer electrolytes according to Example 1 to obtain a plastic coating composition, and a biaxially stretched polypropylene film coated with the composition was prepared in Example 1.
obtained in the same way. The compositions of these coating compositions and the properties of the coated films are shown in Table 3.

【table】

【table】

[Table] Example 7 800 parts of water containing 13.5 parts of hexadecyltrimethylammonium chloride as an emulsifier was charged into the same polymerization vessel as in Example 1, heated to 90°C with stirring, and the following additives and At the same time, the mixture was added dropwise over a period of time while maintaining the temperature at 90°C. Additives (monomer composition) St...270 parts BA...1.04 parts HEMA...67.5 parts DEAEMA...9 parts (Molecular weight regulator) t-dodecyl mercaptan
...3.5 parts Additive (before polymerization starts) 2,2'-azobis(2-amidinopropane) hydrochloride
...2.3 parts Water ...120 parts After the completion of the dropwise addition, the polymerization container was kept at 90°C for an additional 30 minutes and then cooled. Ta. Solid content of this acrylic copolymer aqueous dispersion
To 100 parts, 4 parts of ECR-34 (Dow Chemical Company), which is a cationic conductive polymer electrolyte, was added as a solid content. This aqueous dispersion was diluted with water to give a solids concentration of 20% to obtain a composition for coating plastics. A biaxially oriented polypropylene film coated with this coating composition was obtained in the same manner as in Example 1. Heat seal strength of this coating film (g/15
mm) is 80 at 90℃, 100℃ and 110℃, respectively.
100 and 110, and the charging characteristics are charging voltage 4.7mV,
The half-life was 1.3 seconds. Example 8 The materials charged into the polymerization container were 870 parts of water containing 90 parts of a 30% by weight aqueous solution of Elecondo PQ-A (Soken Chemical Co., Ltd.), which is a conductive polymer electrolyte, and the additives and the following substances. The second-order transition temperature was 46.5°C, the average molecular weight was
A composition for coating plastics having an acrylic copolymer of 32000 was obtained. Additives (monomer composition) St...122 parts MMA...122 parts EA...140 parts HEMA...68 parts (molecular weight regulator) t-dodecyl mercaptan
…1.5 parts Additive (polymerization initiator) Potassium persulfate …2.3 parts Water …120 parts A natural wax dispersion (solid content
20% by weight) and 1.35 parts of finely powdered silica were blended. A biaxially oriented polypropylene film coated with this coating composition was obtained in the same manner as in Example 1. Heat seal strength of coating film (g/15mm)
were 70, 95 and 110 at 90°C, 100°C and 110°C, respectively, and the charging characteristics were a charging voltage of 5.7 mV and a half-life of 1.8 seconds.

Claims (1)

[Claims] 1 (A) (a) an α,β-unsaturated carboxylic acid having one or more carboxyl groups and/or
0 to 10% by weight of one or more of the salts, and (b)
one or more acrylic acid alkyl esters (the alkyl group of which has 1 to 12 carbon atoms) and/or methacrylic acid alkyl esters (the alkyl group of which has 1 to 12 carbon atoms) A copolymer comprising 10 to 98% by weight of one or more types, and further 0 to 80% by weight of (c) one or more copolymerizable vinyl monomers, if necessary. If the average molecular weight of the copolymer is 5000
~150,000 and a secondary transition temperature of 20 to 100°C, based on 100 parts by weight of the solid content of an aqueous acrylic copolymer dispersion containing substantially particles of a copolymer (B)
Contains 0.5 to 15 parts by weight of one or more conductive polymer electrolytes containing at least one of carboxyl groups, sulfonic acid groups, quaternary ammonium groups, and/or salts thereof in the molecule. Composition for coating plastics. 2 As copolymerizable vinyl monomers, α, β-
A composition for coating plastics according to the claims, comprising 0.1 to 30% by weight of a hydroxyalkyl ester of an unsaturated carboxylic acid.