JPS61275319A - Water-based coating composition - Google Patents

Abstract

PURPOSE:A water-based coating composition which can give a heat-sealing property to resin films, obtained by polymerizing an acrylic monomer mixture in a dispersion obtained by polymerizing an electroconductive sulfonate salt- containing vinyl monomer in water. CONSTITUTION:0.5-20pts.wt. monomer mixture comprising 100-25wt% elec troconductive sulfonate salt-containing vinyl monomer (e.g., sodium p- styrenesulfonate) and 0-75wt% copolymerizable vinyl monomer is polymerized in a water medium. 0-10wt% carboxyl group-containing alpha,beta-unsaturated carboxylic acid (salt), 10-98wt% 1-12C alkyl (meth)acrylate and 1-30wt% monomer of the formula (wherein R1 is H or CH3), obtained by adding epsilon- caprolactone to a hydroxyalkyl (meth)acrylate are polymerized in the above obtained dispersion to obtain the purpose water-based coating composition comprising an aqueous dispersion containing particulate copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an aqueous coating composition, and more particularly, to a composition for polymerizing an acrylic mono-fi monomer mixture in an aqueous medium containing a conductive copolymer. plastic film (hereinafter referred to as ■)
The present invention relates to an aqueous coating composition comprising an aqueous acrylic copolymer dispersion that can be applied to a film (abbreviated as "film") using an aqueous medium and can impart heat-sealing properties to the film.

(Prior art) With the spread of automatic packaging machines in recent years, there has been an increasing demand for films that can be wrapped continuously and have both heat-sealability and antistatic properties, and various proposals have been made for manufacturing methods for this type of film. is being done.

An effective method for imparting heat-sealability and antistatic properties to a film is to apply a coating agent that imparts these properties to the film. By coating a film with an aqueous dispersion containing a conductive vinyl monomer having a sulfonate or the like as disclosed, sealing properties and antistatic properties can be imparted.

<Problems to be Solved by the Invention> However, as the packaging speed of automatic packaging machines has recently become even faster, static electricity is generated in the film, making it more likely to be charged. It has become necessary to provide antistatic properties.

(Structure of the Invention) That is, the present invention provides: 100 to 25% by weight of one or more conductive vinyl monomers having a sulfonic acid salt as component A, and vinyl monomers O to copolymerizable therewith. Single ω body mixture consisting of 75% maximum 0.5
~20.0 double opening, as component B (a) 0 to 10% by weight of one or more β-unsaturated carboxylic acids and/or salts thereof having one or more carboxyl groups; , and (b) 10 to 98% by weight of one or more of (meth)acrylic acid alkyl esters (the alkyl groups thereof having 1 to 12 carbon atoms), (c) hydroxyl of (meth)acrylic acid 1 part to 30 mff of a monomer obtained by adding ε-prolactone to an alkyl ester, and if necessary, (d) one or more copolymerizable vinyl monomers (0 to 80 parts). 100 parts by weight of a wet mixture of IF' and 100 parts by weight consisting of 100 parts by weight of an IF' wet mixture consisting of 100 parts by weight of a copolymer obtained by polymerizing component B in a dispersion obtained by previously polymerizing component A in an aqueous medium as particles. An aqueous coating composition comprising an aqueous dispersion.

Examples of the conductive vinyl monomer for the sulfone M salt used in the present invention include monomers shown in general formulas (1) to (II).

However, in the formula, m=o, 1 M=Li, Na, etc. (1) 7 /L, potash metal or NH4 general formula (II) do.

However, in the formula, m=0.1 n=1-4 R1-H or C]13 M=alkali metal such as Li, Na, or NH4 Among these, p-styrene sulfone in the category of general formula (I) Sodium or ammonium salts of acids and sodium vinylbenzyl sulfonate can be particularly preferably used.

In the present invention, the conductive vinyl component A is added in an amount of 0.5 to 20.0 parts by weight, preferably 2.0 to 10.0 parts by weight, per 100 vehicle Id parts of the B component. is required, and if the Ia degree is less than 0.5 parts by weight, antistatic properties will not be exhibited. On the other hand, if it exceeds 20 m ffi parts, the viscosity of the aqueous dispersion increases, polymerization stability deteriorates, and blocking resistance decreases, which is not preferable.

There are no particular restrictions on the vinyl monomer that can be copolymerized with the conductive vinyl monomer, but it is desirable to have a composition that is the same as or close to the composition of the monomer of component B.8. This increases the compatibility between the conductive polymer and the component B copolymer, resulting in improved heat sealability and a coating composition with excellent transparency. In general, blocking resistance is improved by using a monomer composition that provides a polymer with a high secondary transition temperature, such as a copolymerizable vinyl monomer.

The proportion of the vinyl monomer copolymerized with the conductive vinyl monomer is 0 to 15% by weight, preferably 20 to 67% by weight. When this ratio exceeds 20% by weight or more, the resulting copolymer is not completely soluble in water, resulting in a coating film with good water resistance and blocking resistance. If it exceeds 75% by weight, the antistatic effect decreases, which is not preferable.

The coating composition of the present invention can be produced by using the homopolymer or copolymer of these conductive vinyl monomers as a dispersion stabilizer by utilizing the property that the dispersion stability is improved in the dispersion combination. Although the resulting composition does not substantially contain an emulsifier, a small amount of a general emulsifier or protective colloid may be added as an auxiliary if necessary.

The α,β-unsaturated carboxylic acid or its salt having one or more carbo-4disyl groups (a) used in the 1llfft mixture as component B of the present invention is, for example, acrylic acid. , methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, maleic anhydride, or alkali metal salts or ammonium salts thereof. Also 2
When using an α,β-unsaturated carboxylic acid or a salt thereof having at least 1 carboxyl group, its hafester may be used. These carboxylic acids or salts thereof mainly have the effect of improving adhesion to the film, and the amount used is preferably 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.

In addition, (b) (meth)acrylic acid alkyl ester is, for example, alkylsopropyl, n-butyl, iso-butyl, amyl, n-
-(meth)acrylates such as hexyl, 2-ethylhexyl, and lauryl groups. 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. In particular, they are used in appropriate combinations in consideration of the secondary transition temperature. The amount used is preferably 10 to 98% by weight.

Further, the monomer (c) in which ε-caprolactone is added to a hydroxyalkyl ester of (meth)acrylic acid is a monomer represented by general formula (III).

General formula (I[[) However, in the formula, m = 1 to 4 n≧1 R1 = H or C113 Among the monomers represented by general formula (■), 2-bitroxyethyl (meth)acrylate has ε - Turnip [1 colactone]
~10 mol (i.e. J3 in general formula (III) and n=1~
10) The added material is easily available in the T industry, is easy to handle, has good compatibility with the monomer used in the present invention and the polymer made of the monomer, and therefore has a good appearance. This is preferred because the membrane can be reduced to 19%.

The amount of monomer (c) used is 0.1 to 30% by weight, preferably 1 to 15% by weight. If it is less than 0.1% by weight (c
) monomers have little effect, and when used in excess of 30% by weight, the appearance of the resulting coating film may be impaired.

The antistatic property exhibited in the coating film of the aqueous coating composition of the present invention is thought to be mainly due to the ion conduction mechanism of electricity by the conductive vinyl monomer moiety having the sulfone VT salt. The contribution of water M groups etc. is thought to be small. However, the monomer () not only improves the adhesion of the aqueous coating composition to the film, but also improves the adhesion of the aqueous coating composition to the film. The use of monomer (c) in conjunction with a conductive vinyl monomer having a l-salt results in a film coated with an aqueous coating composition, which is not expected from a hydroxyalkyl Nisdel of an α,β-unsaturated carboxylic acid. The effect of improving antistatic properties is exhibited.

In addition, the monomer (c) is located at a position away from the polymer main chain,
Since polymers containing highly chemically reactive primary hydroxyl groups are formed, it is easy to perform polymer reactions using this water ILM, such as melamine resins, isocyanate compounds, epoxy compounds, etc. It is advantageous when cross-linking using a cross-linking agent.

Next, as the vinyl monomer of (d), the following (i) to (Vi
Examples include, but are not limited to, ii).

(i) Vinyl-substituted aromatic hydrocarbons such as styrene and α-methylstyrene.

(ii) α of acrylonitrile, methacrylonitrile, etc.
, β-unsaturated aliphatic tolyls (+++) organic acid vinyl esters such as vinyl acetate and vinyl propionate.

(iv) Vinyl halides such as vinyl chloride and nylidene chloride.

Further, as a monomer having a reactive functional group, (V) α,β-unsaturated carboxylic acid amides such as acrylamide, methacrylamide, and N-me1-xyacrylamide.

(vi) 2-hydroxyethyl (meth)acrylate,
α such as 2-hydroxypropyl (meth)acrylate,
Hydroxyalkyl esters of β-unsaturated carboxylic acids.

(vii) Monomers having epoxy groups such as glycidyl (meth)acrylate and glycidyl allyl ether.

(viii) α of dimethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, etc.
, aminoal 4-yl esters of β-unsaturated carboxylic acids.

These copolymerizable vinyl monomers may be used singly or in combination of two or more, if necessary. The amount used is preferably 0 to 80%. These factors are considered to mainly affect the hardness, blocking resistance, and secondary transition temperature of the resulting coating film.

The target acrylic copolymer has an average molecular weight of 5,
000 to 150,000, preferably a, ooo to 8
0,000 and a secondary transition temperature of 20 to 100°C, preferably 25 to 10°C. Average molecular weight is s, ooo
If it is less than that, it will be difficult to exhibit the characteristics as a coating film,
Sufficient heat seal strength cannot be obtained. 150.000
If it exceeds this value, the adhesion to the film will decrease and the viscous flow characteristics necessary to obtain good heat sealing properties will be lost. In addition,
The average molecular weight here is the number average molecular weight. Moreover, if the secondary transition temperature is less than 20° C., the coating film exhibits tackiness even at room temperature and causes blocking. If the secondary transition temperature is 100° C. or higher, the coating film will be hard, the flexibility will be reduced, and the heat sealability will be impaired.

These copolymers are synthesized as aqueous dispersions containing essentially particles. The "substantially particles" may be particles that are recognized as M1 under an electron microscope.

Next, a method for producing the aqueous coating composition of the present invention will be described.

Conductive vinyl monomer with sulfonate 100-25
0.5 to 20.0 parts by weight of water per 100 weight % of component (B), a monomer mixture of 0 to 75 weight % of a vinyl monomer copolymerizable with this Polymerizes in medium. Note that the polymerization system is preferably substituted with nitrogen or the like to remove oxygen.

As a polymerization initiator, t-butyl hydroperoxide,
2,5-dimethyl-2,5-di(dobdelbenzyloxy)hexane, peroxides such as hydrogen peroxide, potassium persulfate, ammonium persulfate, and redox systems by combining these polymerization initiators with various reducing agents. Polymerization is carried out using an initiator and a water-soluble azo compound such as 2-2 azobis(2-amicisopropane) hydrochloride.
can be started.

Polymerization temperature, pressure in the polymerization system, stirring method, type of initiator,
It should be selected depending on the type and combination of monomers. The polymerization temperature is generally preferably 20 to 85°C when a redox initiator is used, and 40 to 120°C when a peroxide or azo initiator is used.

In the presence of the copolymer thus obtained, the monomer U compound of component B and an initiator are added and polymerized in an aqueous medium. The initiator and polymerization temperature used in this case may be the same as those used in producing a copolymer containing a conductive vinyl monomer, but they do not necessarily have to be the same.

The aqueous dispersion obtained in this way is stable as it is, but depending on the situation, it is better to adjust the pH with an alkaline substance such as ammonia, sodium hydroxide, potassium hydroxide, diethylamine, jetanolamine, triethylamine, etc. Stability is improved and it is suitable. In addition, hot slip agents such as colloidal silica and talc, anti-blocking agents such as natural waxes and fatty acid amides, antifogging agents, thickeners, stabilizers, etc. may be added to the aqueous coating composition as necessary. good.

(Use of the invention) The aqueous coating composition of the present invention is suitably used for coating films, and the target films include, for example, polyolefin films such as polyethylene films and polypropylene films, borisdylene films, They are polyvinyl chloride film, polyamide film and polynisder film. These films may be unstretched or stretched, but it is particularly effective to use the aqueous coating composition of the present invention on biaxially oriented polypropylene films. Further, it is desirable to apply the aqueous coating composition of the present invention after the film surface has been subjected to a surface treatment such as a corona discharge treatment or an oxidation treatment.

Various methods can be applied to apply the aqueous coating composition of the present invention to a film. For example, a method such as coating and drying using a coating device such as a roll coater, dip coater, gravure coater or spray coater can be used. The coating amount is generally about 0.1 to 5 g of copolymer per 1'wt of film. Since the aqueous coating composition of the present invention used for such a film uses water as a medium,
There is no problem with residual solvent in the film, and it has excellent antistatic properties and binding-one-sealing properties, making it especially suitable for the outer packaging of cigarettes, caramel, chocolate, etc., which are packed using high-speed overlapping automatic packaging machines. It is not only particularly suitable as a packaging material, but also as a general packaging film.

Furthermore, the aqueous coating composition of the present invention can be used in many applications other than packaging films by taking advantage of its properties, such as antistatic properties (electroconductivity), such as masking films,
It can be used as a material for photolithography such as lithographic film, for dustproofing and antistatically copying materials, or as a conductive layer material for electrostatic recording sheets.

In addition to plastic films, the aqueous coating composition of the present invention can also be used as a coating agent and antistatic agent for metal foil, paper, cellophane, plastic products, leather, etc., and can also be used for paper, cloth, plastic films, etc. It can be used as an adhesive for laminating metal foil, etc., or as a heat protectant.

The present invention will be further explained in Examples. In the Examples and Comparative Examples, unless otherwise specified, % indicates weight %.

The performance of the coated film obtained in Examples and Comparative Examples J3 is the value determined by the following measuring method.

Charging characteristics: Using a static honest meter (Shishido Shokai), a voltage of 10V was applied, the temperature was 20℃,
The attenuation half-life time of the charged voltage was measured in an atmosphere with a humidity of 65% R11.

Heat-sealing strength: The film-coated surfaces were put together and heat-sealed for 1 second at 120° C. and a pressure of 1 g/cd using a bar-type heat sealer. This film was placed in an atmosphere with a temperature of 20°C and a humidity of 65% for 24 hours.
After the film was allowed to stand for a period of time, the force required to peel off the film at a speed of 100 mm/min was measured using a tensile tester MllI.

Coefficient of friction: 65mm x 61 with film attached
．． A 5 mm metal plate is passed over a fixed film surface at a tensile speed U of 150 m11/ff1 in,
The dynamic friction coefficient and static am coefficient between the coated surfaces of the film were measured.

Blocking resistance: Layer the coated surfaces of the films together, under an atmosphere of temperature 40°C and humidity 80% R11, 5
After being left for 48 hours under a load of 0.00 (]/ci), the film was cooled to room temperature in fJIL.A film with no blocking was accepted as a pass.

Second-order transition temperature: The second-order transition temperature of each iat homopolymer used in the copolymerization was calculated using the following calculation formula using a needle tube. (Translated by Shigeharu Onoki, Mechanical Properties of Polymer Composites, Kagaku Dojin Co., Ltd. (1976). However, 1. r: Secondary transition temperature of copolymer ('k) T3
1L: Secondary transition temperature W of the homopolymer of component a: a
Component weight fraction T, 14: Secondary transition temperature W of homopolymer of component b:
Weight fraction of component b The following numerical values were used for the secondary transition temperature of the homopolymer of each camellia body.

Acrylic acid: 379°C Ethyl acrylate: 251°C Methyl methacrylate: 378°C Hydroxyethyl methacrylate: 328°C Styrene: 373°C Plaxel FM2: 245°C 2 with reflux condenser 4, thermometer, stirring bar, and dropping funnel
ft Paraple flask with 961 g of water, component A below, and 0.1 g of t-dodecyl mercaptan as a molecular weight regulator.
While stirring under a nitrogen atmosphere, the temperature was raised to 85°C. Add 0.29 parts of potassium persulfate to this and 180 parts of water.
and polymerize for 20 minutes. Next, a mixture of the following ingredients and 4.4 g of t-dodecyl mercaptan and an aqueous solution of 2 g of potassium persulfate dissolved in 162 g of water were each dropped over a period of 2 hours from separate dropping funnels.

After completion of the dropwise addition, the mixture was kept at 85° C. for 3 hours, and then cooled.

(Component A) (Conductive vinyl monomer) Sodium p-styrene sulfonate 27 (1 (copolymerizable vinyl monomer) Plaxel FH-2 (manufactured by Daicel Chemical Co., Ltd.: ε to 2-hydroxyethyl methacrylate) -monomer with 2 moles of caprolactone added) 1.51;1 acrylic acid
0.2g methyl methacrylate
2.7g ethyl acrylate
2.9g Styrene 2.7g (
Component B] A mixture having the same composition as the copolymerizable vinyl monomer of Component A 440Q The solid content of the aqueous dispersion thus obtained is 30%, pl+
2.1, and the viscosity was 23 cps/30°C.

5 parts by weight of natural wax, 0.3 parts by weight of silica, and 0.03 parts by weight of colloidal silica are blended with 100 parts by weight of the solid content of this anionic aqueous dispersion, and water is further added to reduce the solid content. 20%. The above compounded solution was applied to a corona discharge treated biaxially oriented polyp D pyrene film No. 5
It was coated using a bar coater and dried at 105°C for 2 minutes. The coating m of the obtained coated film was 0.9 (1/cf
It was fl. Table 2 shows the properties of this coated film.

Note that Table 1 shows the composition ratio of each component in each Example and Comparative Example.

Further, the abbreviations in Group 1 are as follows.

Na5S: Sodium p-styrene sulfonate FM
-2: Monomer with 2 moles of ε-caprolactone added to 2-hydroxyethyl methacrylate FM-7: ε-caprolactone added to 2-hydroxyethyl methacrylate
- Monomer FA-2 with 7 moles of caprolactone added; ε- to 2-hydroxyethyl acrylate
Monomer AA with 27 additions of cabrolac[·n: acrylic acid MMΔ; methyl methacrylate EA; ethyl acrylate ST; styrene HEMΔ; methacrylic acid 2-hydro: I in the diethyl A component! An acrylic copolymer was prepared in the same manner as in Example 1, except that the amount of electrically conductive vinyl monomer and its usage amount, the composition of 964 copolymerizable vinyls in component A, and the composition of component B were as shown in Table 1. An aqueous dispersion was obtained.

This aqueous acrylic copolymer dispersion was blended with wax, silica, and finely powdered silica in the same manner as in Example 1, and the solid content was further adjusted to 20%, followed by corona discharge treatment in the same manner as in Example 1. A coated film was obtained by coating on a biaxially oriented polypropylene film.

Its properties are not shown in Table 2.

Comparative Examples 1 to 2 The conductive vinyl monomer in component A and its usage amount, the copolymerizable vinyl monomer in component A and the composition of component J and B were used as shown in the table, and the others were An aqueous acrylic copolymer dispersion was obtained in the same manner as in Example 1. Comparative Example 1 is an aqueous dispersion containing a monomer in which ε-caprolactone is added to hydroxyalkylnisdel of (meth)acrylic acid and hydroxyalkylnisdel of (meth)acrylic acid, and Comparative Example 2 is an aqueous dispersion containing no hydroxyalkylnisdel of (meth)acrylic acid. This is a monomer-free aqueous dispersion in which ε-caprolactone is added to a hydroxyalkyl ester of meth)acrylic acid.

This acrylic copolymer aqueous dispersion was blended with wax, silica, and finely powdered silica in the same manner as in Example 1, and the solid content was further adjusted to 20%, followed by a discharge treatment in the same manner as in Example 1. A coated film was obtained by coating a biaxially oriented polypropylene film.

Its properties are shown in Table 2. i.

As is clear from Table 2, the films of Examples 1 to 5 coated with the composition containing the monomer to which ε-caprolactone was added had less electrification, and their decay rate was faster.
Moreover, the heat sealing strength is also high, and it can be seen that the other properties are excellent without being impaired.

Claims (1)

[Scope of Claims] Component A consists of 100 to 25% by weight of one or more conductive vinyl monomers having a sulfonate salt, and 0 to 75% by weight of a vinyl monomer copolymerizable therewith. The monomer mixture becomes 0.5
~20.0 parts by weight, as component B (a) α having one or more carboxyl groups;
, 0 to 10% by weight of one or more β-unsaturated carboxylic acids and/or salts thereof, and (b) (meth)acrylic acid alkyl ester (the alkyl group thereof is 1 to 12
10 to 9 of one or two or more of the following:
8% by weight, (c) 1 to 30% by weight of a monomer obtained by adding ε-caprolactone to a hydroxyalkyl ester of (meth)acrylic acid, and if necessary, (d) a copolymerizable vinyl monomer. 0 to 80% by weight of one or more of the following:
An aqueous dispersion consisting of 100 parts by weight of a monomer mixture consisting of 100 parts by weight and containing substantially particles of a copolymer obtained by polymerizing component B in a dispersion obtained by previously polymerizing component A in an aqueous medium. An aqueous coating composition comprising: