JPH03202135A - Emulsifier for microcapsule, microcapsule using same emulsifier and its preparation and carbonless pressure-sensitive copy paper using same microcapsule - Google Patents

Abstract

PURPOSE:To obtain a high strength microcapsule using a small amount of a film material by forming the microcapsule having a wall film composed of an aminoaldehyde condensate in an aqueous medium containing a water-soluble polymer composed of a copolymer of specific monomers. CONSTITUTION:Predetermined amounts of benzyl (meth)acrylate, styrene having an alkyl substituent and maleic anhydride are copolymerized by emulsion polymerization to synthesize a terpolymer. A microcapsule is formed in an aqueous medium containing the terpolymer using an amino-aldehyde condensate as a wall film material. A coating solution is prepared by compounding the microcapsule including an electron donating color former, a buffering agent and a binder and applied to a support such as acidic paper or neutral paper and dried to obtain carbonless pressure-sensitive copy paper.

Description

Detailed Description of the Invention (A) Industrial Field of Application The present invention relates to an emulsifier for microcapsules, a method for producing microcapsules using the emulsifier, a microcapsule obtained by the production method, and a method using the microcapsule. This is applied to carbonless pressure-sensitive copying paper.

■ Conventional technology Microcapsules are microcapsules that contain liquid, solid, or gas as fine particles ranging in size from 1 micron to several white microns, and are uniformly covered with a thin film. Microcapsules for colorless and colored dyes, chemicals, pesticides, fragrances, feeds, etc. have been commercialized industrially.

The most common application is to pressure-sensitive copying paper, in which (1) a colorless electron-donating dye is dissolved in an organic solvent such as diphenylalkane, contained in microcapsules, and placed on a support. This is the so-called top paper. (2) A base paper coated with an electron-demanding color developer on another support, and (
3) A combination of upper paper and lower paper, clay paper, which is used by combining microcapsules containing a colorless electron-donating dye on one side of the support, inner paper coated with a color developer on the other side, etc. When used in combination with middle paper and bottom paper, if the microcapsule layer and color developer layer are brought into contact and pressure is applied to a local area, the microcapsules in that area will be destroyed and the colorless dye will be formed. The color developer causes a reaction,
Color is developed in the developer layer.

For application to pressure-sensitive copying paper other than air, (4) the above-mentioned microcapsules and developer are coated on the same side of the support; or (5) the above-mentioned microcapsules and developer are coated on the same side of the support. There are products that contain one coloring agent and coated with the other. Even when these sheets are used alone, the pressed portion develops color and can be used as recording paper, and it is also possible to copy and record a plurality of sheets by stacking them.

In this way, by forming m* on the outside of a substance with a certain characteristic, microcapsules can simultaneously confine that characteristic, and when necessary, the encapsulated substance can be taken out by breaking the membrane. It is possible.

Conventionally known methods for producing microcapsules include: (1) Coacervation method using an ionic complex of gelatin and anionic protective colloid.

(2) An interfacial polymerization method that utilizes a film-forming reaction at the interface between the internal and external phases.

(3) 1n-situ method (Japanese Patent Publication No. 60-210
0, JP 53-84881, JP 54-25277, JP 54-49984, JP 55-47139, JP 56-51
238, 59-177129) is known.

The encapsulation method described above yields microcapsules with a dense film that protects the encapsulated substances and is widely applied industrially, but there are many problems in terms of production and quality. It is also true that the country has

That is, in the coacervation method, (1) the pH, temperature, time, and operation involved in the reaction are complicated;

(Since it is difficult to obtain a microcapsule slurry with a concentration of 2120% or higher, a large amount of water must be evaporated when used for pressure-sensitive copying paper, so there is great room for improvement in terms of work speed and energy cost.

(3) Since the membrane material is a natural product, there are large fluctuations in quality and price.

(4) It cannot withstand long-term storage because it has a tendency to rot and agglomerate.

It has the following problems.

Regarding the interfacial polymerization method, although the problem with the acervation method has been improved to some extent, it is not suitable for encapsulating unstable substances because the highly reactive film base material is reacted (at a relatively high temperature). .

Furthermore, there are still areas to be improved regarding solvent resistance and water resistance.

In the n-8 itu method, encapsulation with various amine resins has been proposed and is currently widely applied industrially, but it is also true that it has the following problems.

(1) Since the water-soluble polymer substance that emulsifies the hydrophobic liquid into microscopic particles has a relatively high viscosity, the obtained microcapsule dispersion also inevitably has a high viscosity, and has a good solid content of 50% or more. It is virtually difficult to obtain a fluid microcapsule slurry.

+21 Water-soluble polymer substance with low viscosity compared to (1),
Alternatively, when a water-soluble polymer whose viscosity has been reduced by diluting it with an appropriate solvent is used as an emulsifier, the emulsion stability of the hydrophobic liquid decreases and aggregation or coagulation of the hydrophobic liquids occurs.

(3) In order to obtain high physical and chemical film strength and stability, it is necessary to use high temperature reaction conditions or to add a large amount of film material. Adopting an encapsulation method that is sensitive to such fluctuations in conditions can easily result in defective products in industrial manufacturing, especially due to slight errors in setting conditions or unexpected changes in conditions. is narrowed down.

Furthermore, when microcapsules obtained by conventionally known manufacturing methods are used in carbonless pressure-sensitive copying paper, static pressure color development stains and heat resistance are not sufficient.

(C) Problems to be Solved by the Invention The present invention aims to solve the problems in the conventionally known microencapsulation methods shown in item 0. Include as 1
It is an object of the present invention to provide a water-soluble polymer emulsifier suitable for a method for producing microcapsules by an n-situ method. Furthermore, the above emulsifier is used, and 1n-si
By adopting the tu method, the purpose is to obtain microcapsule slurry with a high solid content concentration and moderate viscosity, and to provide microcapsules that can have a stronger film than b with a small amount of film agent used. .

A further object of the present invention is to provide a carbonless pressure-sensitive copying paper which is excellent in resistance to static pressure staining and heat, using microcapsules produced by an improved manufacturing method.

(b) Means for Solving the Problems The present invention provides an emulsifier for microcapsules containing a water-soluble polymeric substance as an active ingredient, in which the water-soluble polymeric substance is (A) benzyl (meth)acrylate, (i) an alkyl substituted The emulsifier for microcapsules is a multicomponent copolymer obtained by copolymerizing monomers containing styrenes having a group and maleic anhydride, and more preferably the monomer composition of the multicomponent copolymer is (A) Benzyl (
This is an emulsifier for microcapsules containing 0.1 to 50 mol% of meth)acrylate, 5 to 59.9 mol% of styrenes having an alkyl substituent, and 40 to 50 mol% of maleic anhydride.

Styrenes having an alkyl substituent used in the present invention include α-methylstyrene, β-methylstyrene,
Vinyltoluene, nuclear alkyl-substituted α-alkylstyrene, and the like. Nuclear alkyl-substituted α-alkylstyrenes include nuclear methyl-substituted α-methylstyrene, nuclear ethyl-substituted α-methylstyrene, nuclear isopropyl-substituted α-methylstyrene, etc. (0-, m-, and 0-forms can all be used. ). These styrenes having an alkyl substituent can be used alone or in combination, and α-methylstyrene is the most preferred monomer.

In addition, other monomers may be used in the monomer composition of the multi-component copolymer of the present application as long as the performance as an emulsifier for microcapsules is not deteriorated. Examples include styrene, isobutylene, (meth)alkyl acrylate, Examples include ester, acrylonitrile, acrylamide, and the like.

Furthermore, the present invention provides, in an aqueous medium containing a water-soluble polymer substance,
In a method for producing microcapsules using an aminoaldehyde condensation product as a wall material, monomers containing benzyl (methy)acrylate, styrenes having an alkyl substituent, and maleic anhydride are used as the water-soluble polymeric substance. Regarding a method for producing microcapsules characterized by using a multicomponent copolymer formed by copolymerization, it is more preferable that the monomer composition of the multicomponent copolymer is
(A) 0.1 to 50 mol% of benzyl (meth)acrylate and 5 to 59 mol% of styrenes having 0 alkyl substituents
．． The present invention relates to a method for producing microcapsules, characterized in that the present invention uses an emulsifier for microcapsules containing 9 mol% of maleic anhydride and 40 to 50 mol% of maleic anhydride, and uses an aminoaldehyde condensate as a wall material.

The method for producing the upper air multicomponent copolymer is not particularly limited, and various known methods can be appropriately selected and employed, such as emulsion polymerization, suspension polymerization, solution polymerization, and the like. Preferably, it is obtained by copolymerizing each monomer component in a suitable organic solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc., and then removing the organic solvent. Various known polymerization initiators can be used without particular limitation. In the case of the above solution polymerization method, organic fugitives such as benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy 2-ethyl hequinanoate, azobisisobutyronitrile, dimethyl-2,2'- Organic azo compounds such as azobisisobutyrate are preferably used. In order to use the obtained copolymer as the emulsifier for microcapsules of the present invention, the copolymer may be suitably neutralized with a suitable neutralizing agent, and then diluted and dissolved in water.

There is no particular problem as long as the composition ratio of each composition varies within the upper air range, but if even one of them deviates from this range, undesirable phenomena may occur for the microcapsule manufacturing process and quality obtained. It arises.

Specifically, when the composition ratio of 0-maleic anhydride exceeds 50%, not only does it become difficult to carry out regular copolymerization reactions of each constituent component, but even if the resulting product is used as an emulsifier aqueous solution, it becomes hydrophobic during the emulsification process. separation of hydrophobic liquids, or the presence of giant hydrophobic liquid particles2. In addition, when the composition ratio of maleic anhydride is 40% or less, the copolymerization reaction proceeds relatively smoothly, but the product is
It becomes insoluble in water or causes a severe increase in viscosity, resulting in unfavorable phenomena in the emulsification process. Moreover, if the ratio of styrenes is higher than this range (if the benzyl (meth)acrylate is small), a tough film as described in the present invention cannot be obtained, and conversely, if the ratio of benzyl (meth)acrylate is high, the water-soluble The viscosity of the polymer tends to increase, which is undesirable because it interferes with the emulsification process or results in incomplete capsules.

The molecular weight of the water-soluble polymer used in the present invention measured by gel vermation chromatography is preferably 1,000,000 or less in terms of polystyrene, and the viscosity by a B-type viscometer is 1,000,000 or less.
0%, pt14.20-2000 in aqueous solution at 0.25℃
Preferably, it is in the cps range.

The method for producing microcapsules in the present invention basically consists of the following four steps.

(1) Preparation process of water-soluble polymer 3 (2) Preparation process of core substance (3) Preparation process of aminoaldehyde initial condensate (4)
) In the process of preparing the water-soluble polymer in step (1) of forming aminoaldehyde 11 fat, the concentration of the water-soluble polymer solution is determined by its viscosity and emulsion stability;
A range of 5% is preferred.

The pH of water-soluble products is usually set in the acidic range of 7 or less,
Preferably, it is used at 6F or higher.

To adjust the pH, a base such as sodium hydroxide, potassium hydroxide, or ammonium, or an acid such as acetic acid, hydrochloric acid, or oxalic acid is used.

(Specifically, various dyes, pharmaceuticals, agricultural chemicals, liquid crystals, fragrances, pigments, etc. are used as the core material of '2J, dissolved or dispersed. Especially when used as a microcapsule for pressure-sensitive copying paper, the core material is used as a core material. An electron-donating coloring agent (organic colorless dye) is used, and its solvents include diarylalkane, alkylnaphthalene, dibenzylbenzene derivatives, alkylbenzene, paraffin, cycloparaffin, chlorinated paraffin, and various esters. 4 Examples include mineral oil and vegetable oil.

As the aminoaldehyde resin (3), urea-formalin resin, melamine-formalin resin, benzoguanamine resin, butylated melamine resin, and butylated urea resin are known, but melamine-formalin resin is particularly preferred. It will be done.

The initial condensate of these resins used in (3) can be easily obtained by reacting the corresponding monomers with each other at an appropriate temperature under (1N, ii) conditions, but ready-made commercially available products may also be used. .

These aminoaldehyde initial composites and an oil-soluble liquid serving as a core material are generally added in a weight ratio of 1:3 to 1:40, but are not necessarily limited to this. It may be used with appropriate changes depending on the material type or purpose. Instead of the above-mentioned initial composite, corresponding simple substances (monomers) may be used. Note that this step (3) may be omitted depending on the raw materials used and is not essential.

(4) Resin formation process of aminoaldehyde resin, ie, 5. That is, the reaction process is generally carried out at a temperature range of 50 to 90°C, and the resin formation reaction is usually completed in 1 to 3 hours. a catalyst that accelerates the reaction during the resin formation, and after the reaction is complete;
There is no problem in using a processing agent containing excessive formaldehyde.

The microcapsule slurry obtained by the method of the present invention has a high concentration, low viscosity, and a strong film. In particular, when used as microcapsules for carbonless paper, the coating workability was extremely good, making it possible to smear at higher concentrations and at higher speeds.

The carbonless pressure-sensitive copying paper of the present invention is obtained by applying the capsule containing the electron-donating coloring agent, the buffer, and the binder of the present invention onto a support. The buffering agent of the present invention is added for the purpose of preventing destruction of microcapsules, and generally wheat starch, potato starch, cellulose fine powder, synthetic plastic pigments, etc. are used, but the type And the amount is not particularly limited. Binder 6 Generally, latex, soluble starch, casein, gelatin, gum arabic, polyvinyl alcohol, methyl cellulose, etc. are used alone or in combination, and are used for the purpose of fixing capsules and buffers on the support. The type and amount thereof are not particularly limited. As the support, acidic paper or neutral paper mainly composed of hillulose fibers is usually used, but synthetic paper may also be used.

■　Example Examples of the present invention are shown below.

Note that all copies in the examples indicate ff11 copies.

Example 1 [Production example of water-soluble polymer] 200 g of methyl isobutyl ketone was placed in a 21-kolben equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and two dropping funnels.
After preparing and raising the temperature to iio~115℃, α
- Methylstyrene 59 g (0.5 mol), benzyl methacrylate 889 (0.5 mol), maleic anhydride 98
A Moazmer solution consisting of 1 mol) and 200 g of methyl isobutyl ketone, and an initiator solution consisting of 2.2 g of tert-butyl peroxybenzoate and 100 g of methyl isobutyl ketone were added dropwise from a separate dropping funnel over a period of 2 hours. It was kept warm for hours. Then, in order to complete the polymerization,
An initiator solution consisting of 2.2 g of tert-butyl peroxy 2-edylhexanoate and 50 g of methyl isobutyl ketone was added dropwise over 30 minutes and held for 1 hour. After cooling the polymerization solution to 100° C. or lower, 150 g of water and 759 (0.9 mol) of 48% caustic soda were added, and then steam was blown in by a conventional method to remove methyl isobutyl ketone. Next, water was added to adjust the solid content concentration to 8% to obtain a water-soluble polymer.

The properties were as follows.

pH = 4.7 Type B viscosity (25°C) = 70 cps [
Microencapsulation 1 3 parts of crystal violet lactone (CVL) as the core material of microcapsules, Hysol SAS I
A solution dissolved in 96 parts of f-296 (aromatic solvent manufactured by Nippon Petrochemical) was prepared.

8 Water-soluble polymer solution 1 obtained in the above production example as an emulsified aqueous solution
To 80 parts, 220 parts of the above hydrophobic liquid was gradually added under strong stirring, and the stirring was continued until the volume average particle diameter became 5 microns to obtain an emulsion.

Separately, 11 parts of melamine, 2 parts of 37% formaldehyde aqueous solution
1.2 parts and 28.2 parts of water were mixed, and sodium hydroxide was added to adjust I) I+ to 9 and heated to obtain an aqueous solution. The melamine-formaldehyde initial condensate aqueous solution was added to the emulsion and stirred for 2 hours at a temperature of 70° C., and the reaction was then completed.

After confirming the formation of microcapsules, the mixture was cooled to room temperature and the EIH was raised to 9.0 using aqueous caustic soda to complete the microcapsule formation.

To 100 parts of the solid microcapsule liquid thus obtained, 30 parts of wheat starch particles and 100 parts of a 10% polyvinyl alcohol aqueous solution were added. The coating liquid was applied to 40g/TrL2 high-quality paper so that the dry coating amount was 5g/m2 to obtain a carbonless pressure-sensitive recording paper top paper (08>). (Mitsubishi NCRC lower paper N-
When typewriter printing was performed in combination with 40,49 Og/TrL2-based bottom paper), a carbonless paper with good color development was obtained.

Example 2 In the production example in Example 1, the monomer composition was changed to 10.49 g (0.1 mol) of styrene, 13.2 g (0.1 mol) of nuclear methyl substituted α-methylstyrene, and 140.8 g (0.1 mol) of benzyl methacrylate. , 8 mol), maleic anhydride 9
The water-soluble polymer was prepared in the same manner except that the amount was changed to 8 g (1 mol).

The properties of the obtained water-soluble polymer are as follows: solid content concentration -7.5%
, B type viscosity (25°C) -120C1)3, p++
=5.0.

Using this water-soluble polymer as an emulsified aqueous solution, encapsulation and creation of a CB sheet were carried out in the same manner as in Example 1.

Example 3 In the production example in Example 1, the monomer composition was 83.29 g (0.8 mol) of styrene, 23.25 g (0,197 mol) of α-methyl 0 styrene, and 0.5259 g (0,197 mol) of benzyl methacrylate. The water-soluble polymer was prepared in the same manner except that maleic anhydride 985F (1 mol) was added.

The properties of the converted water-soluble polymer are as follows: solid content m -8.0%
, Type B viscosity (25°C) = 70 cps, pH = 4
．． It was 8.

Encapsulation and creation of a CB sheet were carried out in the same manner as in Example 1 using this water-soluble polymer as an emulsifier aqueous solution.

Example 4 Urea 14 was added to the hydrophobic liquid emulsion obtained in Example 1.
42 parts of a 37% aqueous formaldehyde solution and 29 parts of a 37% formaldehyde aqueous solution were added thereto, and the mixture was stirred at a temperature of 60° C. for 2 hours to complete the reaction.

After the formation of microcapsules was confirmed by TM, the mixture was cooled to room temperature and the pH was raised to 9.0 with an aqueous caustic soda solution to complete microencapsulation. Next, a CB sheet was prepared in the same manner as in Example 1.

1 Comparative Example 1 [Production of α-methylstyrene-maleic anhydride copolymer aqueous solution 1 In the production example in Example 1, instead of 88 g (0.5 mol) of benzyl methacrylate, α-methylstyrene 5
Example 1 except that 9 g (0.5 mol) was used.
I did the same thing. The properties of the obtained α-methylstyrene-maleic anhydride copolymer water-soluble polymer were as follows: solid content -8%;
Type B viscosity (25°C) = 250 cps, pH = 4.
It was 8.

[Microencapsulation] Using this water-soluble polymer as an emulsifier aqueous solution, Example 1
Water added with melamine-formaldehyde of 28.2
Encapsulation and production of a CB sheet were carried out in the same manner as in Example 1, except that 130.6 parts of water was used instead of 130.6 parts of water.

Comparative Example 2 Conducted on 180 parts of an 8.0% water solution of ethylene-maleic anhydride binary copolymer (trade name EMA-31, manufactured by Monsando, Inc., USA) adjusted to pH = 3.5 as a water-soluble polymer solution. 220 parts of the hydrophobic liquid from Example 1 was added and emulsified in the same manner.

Next, 13 parts of melamine and 2 parts of 37% formaldehyde aqueous solution
A melamine-formaldehyde initial synthesis product was obtained by heating and dissolving 5.1 parts and 132 parts of water at all=9.0, which was added to the above emulsion and stirred for 2 hours at a temperature of 70°C to complete the reaction.

The obtained microcapsule slurry was treated in the same manner as in Example 1 to obtain a carbonless pressure-sensitive copying paper (CB).

A water-soluble polymer was prepared in the same manner as in Example 1 except that the monomer composition was changed to 104 g (1 mole) of sutyrene and 98 g (1 mole) of anhydrous maleic fi.

The properties of the scooped water-soluble polymer are as follows: solid content concentration -7.5%
, Type B packing degree (25°C) = 120 cps, pH =
It was 4°4.

Using this water-soluble polymer as an emulsifier aqueous solution, Example 1
water added with formaldehyde 28.2
Encapsulation and production of a CB sheet were carried out in the same manner as in Example 1, except that 79.4 parts of water was used instead of 3 parts.

The microcapsules and pressure-sensitive copy paper obtained in the Examples and Comparative Examples were evaluated using the following method and used as a criterion.

・Solid content concentration of capsules after dry heat treatment at 105℃ for 3 hours.・Viscosity of capsule emulsion measured at 20℃ using a type 8 packing meter.・Pull, -Spot The solid concentration of capsule emulsion is 20%. Dilute with water so that
9/m2, and after drying, count the number of spots per 100c2. The worse the encapsulation, the higher the number of points, and for practical purposes, 5 or less is preferable.

・Static pressure colored stain CB sheet and C sheet were placed one on top of the other with the coated surfaces facing each other, and static pressure was applied for 30 seconds at a pressure of 20 kg/cm2, then the reflectance of the CF surface was measured.

The larger the value, the stronger the microcapsule film.

- A heat-resistant CB sheet and a CF sheet were stacked so that the coated surfaces faced each other, a light load of 50 g/TrL2 was applied, and the fouling rate for the CF sheet was measured after being left in an atmosphere of 140° C. for 3 hours. The larger the value, the better the heat resistance and the stronger the film.

The reflectance of static pressure colored stains and the heat-resistant OF sheet was measured using a color difference meter ND101DP manufactured by Nippon Heavy Industries, and the display is the reflectance of the colored area/the untreated area and the background area). Reflectance of X100 (%)
It was shown in The results of the evaluation based on the above measurement methods are shown below.
Shown in

Table 1 (0) Effects of the Invention As is clear from the results of the Examples, the present invention was able to provide capsules with high strength and low viscosity and high solid content even with a small amount of membrane material.

In particular, when the method of the present invention is applied to the production of pressure-sensitive copying paper, it is possible to obtain pressure-sensitive paper that has excellent coating suitability65 due to its low viscosity, and has excellent color development and stain resistance. can get.

Furthermore, an unexpected effect obtained with the present invention is that the emulsification time is shortened, and in particular, the time required to prepare the hydrophobic liquid to the desired size is significantly shortened compared to conventionally known methods. You can get the effect of

Claims (6)

[Claims] (1) An emulsifier for producing microcapsules containing a water-soluble polymeric substance as an active ingredient, in which the water-soluble polymeric substance contains (A) benzyl (meth)acrylate, (B) styrenes containing an alkyl substituent, and ( C) An emulsifier for microcapsules, which is a multicomponent copolymer obtained by copolymerizing monomers containing maleic anhydride. (2) The monomer composition of the multicomponent copolymer obtained by copolymerizing monomers containing (A) benzyl (meth)acrylate, (B) styrenes having an alkyl substituent, and (C) maleic anhydride is (A) Claim 1: 0.1 to 50 mol% of benzyl (meth)acrylate, 5 to 59.9 mol% of (B) styrenes having an alkyl substituent, and 40 to 50 mol% of (C) maleic anhydride. The emulsifier for microcapsules described above. (3) In a method for producing microcapsules having an aminoaldehyde condensation product as a wall material in an aqueous medium containing a water-soluble polymer substance, the water-soluble polymer substance (A
) A method for producing microcapsules, comprising using a multicomponent copolymer obtained by copolymerizing monomers containing benzyl (meth)acrylate, (B) styrenes having an alkyl substituent, and (C) maleic anhydride. (4) The monomer composition of the multicomponent copolymer obtained by copolymerizing monomers containing (A) benzyl (meth)acrylate, (B) styrenes having an alkyl substituent, and (C) maleic anhydride is (A) Claim 3: benzyl (meth)acrylate is 0.1 to 50 mol%, (B) styrenes having an alkyl substituent group is 5 to 59.9 mol%, and (C) maleic anhydride is 40 to 50 mol%. The method for manufacturing the microcapsules described. (5) Microcapsules obtained by the method for producing microcapsules according to claim 3 or 4, wherein the wall material is an aminoaldehyde condensation product. (6) A carbonless pressure-sensitive copying paper comprising, on a support, a coating layer containing the microcapsules according to claim 5 containing an electron-donating coloring agent, a buffer, and a binder.