JP2705801B2 - Dispersant for aqueous dispersion production - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dispersant used for producing an aqueous dispersion in which a thermoplastic substance is dispersed in water. The aqueous dispersion of a thermoplastic substance obtained by using the dispersant of the present invention is useful as a coating agent for paper, film, metal foil, an adhesive, a pressure-sensitive adhesive, a binder for ink, and the like.

[Conventional technology]

Manufactures dispersions of thermoplastic substances, such as polyethylene wax, rosin derivatives, low-density polyethylene, and ethylene-vinyl acetate copolymer, dispersed in water using a dispersant such as a surfactant or protective colloid. The way to do this is known.

For example, an emulsion of a rosin derivative is prepared by hot-melting a rosin derivative, a large amount of a surfactant and water with a homomixer and adding water with stirring (Japanese Patent Laid-Open No. 62-49).
No. 905, etc.) Further, the ethylene / vinyl acetate copolymer is first heated and melted, an anionic or / and nonionic surfactant is added and stirred, and then hot water is added and emulsified by a homomixer. (JP-A-57
No. 61035). For the emulsion of petroleum resin, a method is used in which a petroleum resin is melted, an aqueous solution of partially saponified polyvinyl alcohol is melt-kneaded by a pressure kneader or the like, and hot water is gradually phase-inverted and emulsified (Japanese Patent Application Laid-Open No. 54-20065). Gazette).

However, since the aqueous dispersions obtained by these conventional methods use a large amount of a water-soluble surfactant or a protective colloid, the mechanical strength of the dried film may be low or the water resistance may be poor. Often there.

On the other hand, the present inventors have proposed a method for producing an aqueous polymer dispersion using a neutralized product of a specific acrylic copolymer in which such disadvantages have been improved (see JP-A-58-127752).

[Problems to be solved by the invention]

However, when the aqueous dispersion produced by the method described in JP-A-58-127752 was used, it was found that the obtained film had poor low-temperature adhesion and transparency, and its use was limited. An object of the present invention is to provide a dispersant for producing an aqueous dispersion of a thermoplastic material, which solves such problems.

[Means for solving the problem]

In the method described in the above-mentioned publication, the inventors have found that when water and a volatile base of the obtained polymer dispersion evaporate, α, β-non-component which is one component of an acrylic copolymer as a dispersant is used. It is thought that the melt viscosity increases due to the intramolecular or intermolecular association of the saturated carboxylic acid, which hinders the fusion of the emulsion resin particles. As a result of intensive studies on the coalescence, it was found that by introducing polyalkylene glycol methacrylate as the third component, the melt viscosity of the dispersant was reduced, and as a result, an aqueous dispersion having excellent low-temperature adhesion and transparency was obtained. Completed the invention.

That is, the present invention provides a dispersant for producing an aqueous dispersion of a thermoplastic substance, comprising a neutralized product of a copolymer obtained by copolymerizing the following components (A), (B), and (C). Is provided.

(A) Component α, β-unsaturated carboxylic acid 18 to 50% by weight (B) Component α, β-unsaturated carboxylic acid alkyl ester 5 to 50% by weight (C) Component Polyalkylene glycol methacrylate 20 to 75% by weight As the thermoplastic substance dispersed in water to be subjected to the invention, low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer and ester, or a salt thereof, ethylene-methacrylic acid copolymer and its Ester or its salt, ethylene-ethyl acrylate-maleic anhydride copolymer, so-called ethylene-based crystalline ethylene-based copolymer such as ethylene-propylene random copolymer, propylene-hexene copolymer, propylene- Crystalline propylene copolymer mainly composed of propylene such as butene copolymer, polyethylene wax , Ester-based wax, carnauba wax, Fischer-Tropsch wax, microcrystalline wax, paraffin wax and their oxides, low molecular weight polyamide, amide compounds such as fatty acid amide, chlorinated polyethylene, halogenated polyolefin such as chlorinated polypropylene, etc. Thermoplastic substance with melting point of 130 ° C or less; Vicat softening point of polybutylene, polyisobutylene, ethylene-propylene copolymer rubber, liquid polybutadiene and its modified products, ethylene-propylene-diene terpolymer rubber etc. is 130 ° C or less. Rubber substance: compounds having a softening point of 130 ° C. or less according to the so-called tackifier ring and ball method, such as terpene and its derivatives, rosin and its derivatives, petroleum resins and its derivatives, low molecular weight styrene-based resins and their derivatives, and the like. Among them, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / ethyl acrylate / maleic anhydride copolymer,
Carnauba wax, ester wax, terpene derivative, and rosin derivative are preferable because they have appropriate polar groups or an aqueous dispersion with particularly high stability can be obtained.

If the softening point or melting point of these thermoplastics exceeds 130 ° C., the resulting aqueous dispersion becomes amorphous and has a large particle diameter, and the static stability becomes poor.

The dispersant of the present invention for dispersing these thermoplastic substances in water is characterized in that the (A) component, the (B) component, and the (C) component are copolymerized in the above-described ratio, and the carboxyl group of the copolymer obtained is used. It can be obtained by neutralizing a part or the whole with a basic compound.

As the α, β-unsaturated carboxylic acid of the component (A), acrylic acid, methacrylic acid, itaconic acid, citraconic acid, maleic acid, crotonic acid, fumaric acid, monoalkyl maleate and the like can be mentioned. Or may be used in combination. Among these, acrylic acid, methacrylic acid and itaconic acid are preferred from the viewpoint of copolymerizability.

Examples of the (B) component α, β-unsaturated carboxylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and (meth) Examples thereof include lauryl acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, and allyl (meth) acrylate. These may be used alone or in combination. Among these, methyl methacrylate or alkyl ethacrylate having an alkyl group having 6 or more carbon atoms, such as cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, etc. It is preferable that the component (B) has a proportion of not less than 60% by weight in the component (B) because the component (B) has a good affinity for a thermoplastic substance, a good balance between hydrophilicity and lipophilicity as a dispersant, and emulsification. It is particularly preferred because it has a powerful advantage.

The polyalkylene glycol methacrylate of the component (C) is copolymerized with the components (A) and (B) to lower the melt viscosity of the dispersant and to provide the effect of imparting low-temperature adhesion and transparency to the aqueous dispersion. And, for example, polypropylene glycol methacrylate, polyethylene glycol methacrylate, polyethylene glycol polypropylene glycol methacrylate, polyethylene glycol polytetramethylene glycol monomethacrylate, methoxypolyethylene glycol methacrylate, and the like. Is also good. Among them, polypropylene glycol methacrylate, polyethylene glycol polypropylene glycol methacrylate, and polyethylene glycol polytetrafluoroethylene having a molecular weight of 250 or more in terms of the water resistance of the dispersant and the lipophilicity-hydrophilicity are easily balanced. Methylene glycol monomethacrylate is preferred.

These polymerizable monomers of component (A), component (B) and component (C) are used in an amount of from 18 to 50% by weight, preferably from 25 to 50% by weight of component (A).
40% by weight, 5 to 50% by weight of component (B), preferably 10 to 40%
0 to 180 ° C., preferably 40 to 120 ° C. for 0.5 to 20 hours, preferably 2 to 50% by weight in the presence of a polymerization initiator at a ratio of 20 to 75% by weight, preferably 30 to 70% by weight, of the component (C). By reacting for 1010 hours, a copolymer is produced. This copolymer is preferably used in the presence of a hydrophilic solvent such as ethyl alcohol, isopropyl alcohol and cellosolve. Examples of the polymerization initiator include azobisisobutyronitrile, t-butylperoxyisobutyrate, 1,1-bis (t-butylperoxy) cyclohexene, t-butylperoxybenzoate and the like.

When the amount of the component (A) is less than 18% by weight, the hydrophilicity of the neutralized product of the copolymer is weak, and when it exceeds 50% by weight, the hydrophilicity of the neutralized product is too strong to obtain a stable aqueous polymer dispersion. Cannot be manufactured. When the amount of the component (B) is less than 5% by weight, the lipophilicity of the neutralized product of the obtained copolymer is weak, and 50% by weight.
If the ratio exceeds the above range, the lipophilicity of the neutralized product becomes strong, and in any case, a stable aqueous dispersion cannot be obtained. When the amount of the component (C) is less than 20% by weight, the low-temperature adhesion and transparency of the resulting dispersion film are impaired. If it exceeds 75% by weight, a stable aqueous dispersion cannot be obtained because the balance between hydrophilicity and lipophilicity is deteriorated.

The neutralized product of the copolymer used as the dispersant of the present invention can be obtained by neutralizing a part or all of the carboxyl groups in the copolymer with a basic compound. Examples of the basic compound include ammonia or alkylamines such as methylamine, dimethylamine, trimethylamine and ethylamine, alkanolamines such as 2-amino-2-methylpropanol, and morpholine. Above all, when an aqueous dispersion obtained by producing a low-boiling substance such as ammonia or a lower alkylamine having 1 to 4 carbon atoms is dried to form a film, these basic compounds are easily released from the dispersant, so that the film is surrounded by the film. It is preferable because the hydrophobicity of the dispersant increases and the water resistance of the coating improves.

The neutralization reaction is carried out at 20 to 100 ° C for the copolymer and the basic compound.
It is carried out by reacting for 0.1 to 3 hours.

Also, the α, β-unsaturated carboxylic acid of the component (A) is neutralized with a basic compound in advance, and this is added to the component (B),
By copolymerizing the component (C), a neutralized product of the copolymer of the present invention can be produced.

The amount of the basic compound used for neutralization is 10 to 100 mol% of the component (A) constituting the copolymer. If the neutralization is less than 10 mol%, the solubility of the copolymer in water deteriorates, the particle size of the resulting aqueous dispersion increases, and the resin layer and the aqueous layer are separated, which is not preferable.

(Application) The neutralized product is generally adjusted to 5 to 40% by weight with water and used as a dispersant for producing an aqueous dispersion of a thermoplastic substance. The used amount is 2 to 30 parts by weight, preferably 3 to 15 parts by weight in terms of solid content, based on 100 parts by weight of the thermoplastic material to be dispersed.
Used in parts by weight. If the amount is less than 2 parts by weight, a stable aqueous dispersion cannot be produced. On the other hand, if it exceeds 30 parts by weight, the mechanical strength of the film does not endure practical use, and the adhesion of the film to substrates such as paper, aluminum foil, and film is reduced.

The production of an aqueous dispersion of a thermoplastic substance using the dispersant of the present invention is carried out by adding a molten thermoplastic substance to water containing a neutralized substance and uniformly stirring with a homomixer. . The most preferred embodiment is a multi-screw extruder having two or more screws in a casing (Japanese Patent Application Laid-Open No.
No. 2149), and continuously fed from a hopper or an intermediate supply port of the extruder, and heat-melt-kneaded the mixture, and further, a compression zone or / and a measuring zone or / and a degassing zone of the extruder. An aqueous solution of a neutralized substance as a dispersant is supplied under pressure from at least one supply port provided in
By kneading this and the molten thermoplastic substance with a screw, an aqueous dispersion can be continuously produced by extrusion from a die.

Generally, the amount of water used is such that the resulting aqueous dispersion has a solids concentration of 20 to 65% by weight.

An antifoaming agent, a viscosity modifier, an anionic or nonionic surfactant, and an antioxidant may be blended in addition to the above-mentioned neutralized product of the thermoplastic substance and the acrylic copolymer serving as a dispersant.

The aqueous dispersion prepared in this manner has a thermoplastic particle having an average particle diameter of 5 μm or less and a particle diameter of 1 μm or less dispersed in water in a state of 10% by weight or more, preferably 20% by weight or more. And has a viscosity at 25 ° C. of 10 to 10,000 centipoise, preferably 50 to 5,000 centipoise.

This aqueous dispersion is used as a paint, an adhesive, a binder for ink, an adhesive, an adhesive, and a modifier for an emulsion, depending on the type of thermoplastic substance used.

〔Example〕

Next, the present invention will be described more specifically with reference to examples and comparative examples. The percentages and parts in the examples are on a weight basis unless otherwise specified.

Example-1 15 parts of methacrylic acid, 5 parts of acrylic acid, 70 parts of polypropylene glycol methacrylate (Blemmer PP-1000 manufactured by NOF CORPORATION, number of repeating units of propylene glycol unit = 5 to 6), 10 parts of lauryl methacrylate and 10 parts of isopropylate Stirrer, reflux condenser, and 150 parts of alcohol,
The mixture was charged into a four-necked flask equipped with a thermometer and a dropping funnel, and after purging with nitrogen gas, polymerization was carried out at 80 ° C. for 3 hours using 0.6 part of 2,2′-azobisisobutyronitrile as an initiator. Next, after neutralizing with 18.0 parts of a 28% aqueous ammonia solution, water was added to displace while distilling off isopropyl alcohol, and finally, a neutralized product of a viscous acrylic copolymer having a solid content of 30% was obtained. An aqueous solution was obtained (97% yield).

Application Example-1 Ethylene / vinyl acetate copolymer (vinyl acetate content 28
%, Melting point 74 ° C, melt flow rate at 190 ° C
50g / 10min) is continuously supplied at a rate of 100 parts / hour from the hopper of a co-rotating and meshing twin screw extruder (trade name: PCM45φ, Ikegai Iron Works Co., Ltd., three-thread screw shallow groove, L / D = 30). did.

A gear pump (discharge pressure of 3 kg / h) was supplied from a supply port provided in a vent portion of the extruder at a rate of 26.8 parts (solid content: 8 parts) / hour of an aqueous solution of a neutralized product of the acrylic copolymer.
While continuously supplying the product under pressure at a pressure of ² cm ² G), the product was continuously extruded at a heating temperature (cylinder temperature, the same applies hereinafter) of 110 ° C. (screw rotation speed 200 rpm) to obtain a milky white dispersion.

The average particle size of the aqueous dispersion was determined to be about 0.9 μ by a microscope.

This aqueous dispersion was applied on an aluminum foil to a thickness of 5 μm with a bar coater, and heated at 110 ° C. for 2 minutes using a hot air drier to form a film. Upon immersion, no whitening of the film was observed (good water resistance). Furthermore, it is applied on a biaxially stretched polyester film (thickness: 12μ) so as to have a thickness of 3μ after drying with a bar coater, and heated at 150 ° C for 30 seconds using a hot air drier to form a film. The haze measured according to K-6714 was 4.3%.
2.2%). The thickness after drying fine paper weighing 50 g / m ² is 1
The solution was applied with a bar coater so as to have a thickness of 0 μm, and heated at 150 ° C. for 30 seconds using a hot air drier to form a film. Combine the coated surfaces of this coated high-quality paper with a heat sealer, 2k
Heat sealing was performed for 1 second at a pressure of g / cm ² while varying the temperature. The heat-sealed sample was cut into strips of 15 mm width and subjected to a peel test at a peel speed of 300 mm / min with a shopper. The minimum temperature (heat-sealing start temperature) showing strength enough to break the paper was 76 ° C. Met.

Application Examples 2 to 6 and Reference Example 1 Using the dispersant obtained in Example 1, an aqueous dispersion was produced under the same conditions as in Application Example 1 except that various thermoplastic resins shown in Table 1 were used. . The results are shown in the same table.

Examples -2 to 8 and Comparative Examples-1 to 6 Using the monomers shown in Table 2, (meth) acrylic copolymers were obtained, which were treated with the basic compounds shown in the same table as α, β- An aqueous solution of a dispersant was obtained in the same manner as in Example 1 except that all the saturated carboxylic acids were neutralized.

Using this, an aqueous dispersion of an ethylene / vinyl acetate copolymer was obtained in the same manner as in Application Example 1.

The average particle size, water resistance, haze, and heat sealing start temperature of the obtained aqueous dispersion were as shown in Table 2.

 The abbreviations in the table are as follows.

AA: Acrylic acid MAA: Methacrylic acid BMA: Butyl methacrylate LMA: Lauryl methacrylate SMA: Stearyl methacrylate EA: Ethyl acrylate MMA: Methyl methacrylate PE: Polyethylene glycol monomethacrylate PP: Polypropylene glycol monomethacrylate PEP: Polyethylene glycol polypropylene glycol methacrylate PET: Polyethylene glycol polytetramethylene glycol monomethacrylate Application example-7,8 Using the dispersant and ethylene-vinyl acetate copolymer used in Application example-1, ethylene-vinyl acetate copolymer 10
An aqueous dispersion was prepared so as to have the composition shown in Table 3 per 0 parts by weight. This was evaluated in the same manner as in Example-1. The results are shown in the same table.

Claims (1)

(57) [Claims] A dispersant for producing an aqueous dispersion of a thermoplastic substance, comprising a neutralized product of a copolymer obtained by copolymerizing the following components (A), (B) and (C). (A) Component: 18 to 50% by weight of α, β-unsaturated carboxylic acid (B) Component: 5 to 50% by weight of α, β-unsaturated carboxylic acid alkyl ester (C) Component: 20 to 75% of polyalkylene glycol methacrylate weight%