JPS5849570B2 - Hydrophilic foam and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flexible foam with excellent hydrophilicity and a method for producing the same.

As a foam with excellent hydrophilicity, a foam obtained by formalin crosslinking using polyvinyl alcohol as a raw material is well known.

Although this foam has excellent hydrophilicity, it has the drawbacks of being extremely hard in a dry state and having a slow water absorption rate.

In particular, when it is acetalized to improve its mechanical properties in a water-absorbed state, it tends to become even harder when it dries.

On the other hand, as foams that are flexible in a dry state, there are so-called rubber-based foams whose main components are polyurethane, butadiene, or their derivatives, but these are essentially hydrophobic materials and have almost no hydrophilicity.

In order to improve this drawback, hydrophilic monomers are introduced,
Alternatively, methods have been proposed in which polyurethane contains hydrogels with high water absorption, but these methods generally do not significantly improve hydrophilicity, have slow water absorption rates, and deteriorate mechanical properties, and are still unsatisfactory. I haven't gotten what I deserve.

The inventors of the present invention have completed the present invention after intensive studies to improve the various problems described above.

An object of the present invention is to provide a foam that is highly hydrophilic and flexible even when dry.

Another object is to provide a method for manufacturing this foam industrially easily and inexpensively.

The above purpose is to improve the pore walls of the rubber foam by adding 0.2 to 15% by weight of acrylic acids (4), crosslinked u (Hydrophilic foam coated with an acrylic acid copolymer obtained by polymerizing Q, the acrylic acids (4),
A method in which a solution containing a crosslinking agent and an ethylenically unsaturated compound (Q) is applied to a rubber foam and then copolymerized, and a copolymer of the acrylic acid group and the ethylenically unsaturated compound Q and the crosslinking agent C ) is applied to a rubber foam and then copolymerized.

(A) CH2-CR1COOM (B) X-R2-Y (Q CH2-CR3Z (wherein R1, R2, R3, X, Y, Z and M are the same as above) Specific examples of the acrylic acids mentioned above include acrylic acid, methacrylic acid, sodium acrylate, potassium acrylate, and ammonium methacrylate.

Examples of the crosslinking agent represented by the formula (B) include bifunctional compounds that are reactive with carboxyl groups or compounds that have at least two unsaturated groups that are copolymerizable with acrylic acids, such as ethylene glycol diglycidyl. ether, polyethylene glycol diglycidyl ether,
Glycerin diglycidyl ether, epichlorohydrin, ethylenediamine, divinylbenzene, glycidyl acrylate, ethylene glycol diacrylate, N,
Examples include N'methylenebisdiacrylamide.

Furthermore, as the ethylenically unsaturated compound represented by the formula (Q), there are compounds having an unsaturated group copolymerizable with acrylic acids (4), such as acrylonitrile, methyl methacrylate, acrylamide, p-styrenesulfonic acid,
-acrylamide 2-methylpropanesulfonic acid and the like.

Rubber foam is a foam made of a material with so-called rubber elasticity, such as natural rubber, 2T-IJ rubtagene rubber,
Examples include styrene-butadiene rubber urethane, silicone, etc., each of which may be used alone or in combination to form a foam by a conventional method.

Among these, the most suitable material for the purpose of the present invention is a foam made of natural rubber or dibutadiene rubber.

Crosslinked acrylic acid polymers are usually 0% for rubber foams.
．． It contains 2 to 15% by weight, preferably 0.5 to 10% by weight, and more preferably 1 to 7% by weight.

In order to sufficiently increase hydrophilicity and improve durability, the composition ratio is 50 to 80% by weight of acrylic acids and 5% by weight of crosslinking agent.
It is preferred to contain up to 30% by weight of ethylenically unsaturated compounds.

Further, it is preferable to use a foam to which fibroin is added as the foam of the present invention, since the coating strength and water retention of the crosslinked acrylic acid polymer are improved.

It may be added at the time of foaming the rubber foam by mixing it with a certain amount of rubber or by mixing it with acrylic acids and the like to form a coating component.

Covering the pore walls of a foam with a crosslinked acrylic acid polymer is not suitable for a hydrophilic foam if the continuous pores are blocked or the adhesion is localized. It is sufficient to select and use appropriate means.

The foam of the present invention is obtained by applying an acrylic acid or the like to a rubber foam and subjecting it to copolymerization or crosslinking treatment.

Any rubber foam that can be obtained by conventionally known methods can be used, but it is particularly preferable to use foams of natural rubber or dil-IJ rubtadiene rubber that are usually obtained by the following method. be.

It is obtained by mixing an aqueous dispersion of natural rubber or 2-IJ rubtadiene rubber with a crosslinking agent, stirring and foaming the mixture in the presence of a surfactant, and then subjecting it to solidification and crosslinking treatment.

The solid content concentration of the aqueous dispersion of natural rubber or nitrile butadiene rubber is adjusted to 30 to 75% by weight, preferably 50 to 70% by weight, and an alkali metal salt of higher fatty acid, such as calcium oleate, is usually used as a surfactant in the aqueous solution. It is added in an amount of 0.2 to 5% by weight based on the dispersion.

Colloidal sulfur is usually used as a crosslinking agent, and zinc oxide, zinc diethyldithiocarbamate, zinc mercaptobenzothiazole, etc. can be used in combination as a vulcanization accelerator.

Solidification is usually done with sodium silica, followed by 70
The crosslinking process is achieved by heating under saturated steam at ~130°C for 10 to 60 minutes.

When fibroin is added during foam production, the amount added is 1 to 10% by weight, and the addition method is to add and mix an aqueous fibroin solution or an aqueous dispersion of fibroin powder to an aqueous dispersion of natural rubber or nitrile butadiene rubber during foaming. Good.

Fibroin aqueous solution is made by dissolving silk raw materials such as raw silk in calcium chloride, magnesium nitrate aqueous solution, etc. and dialysis-desalting it through a semipermeable membrane. Fibroin powder is made by weakening silk raw materials by acid or alkali treatment, etc. Alternatively, it can be obtained by precipitating and regenerating fibroin from the aqueous fibroin solution and pulverizing it to a particle size of 0.1 to 100 μm.

The foam is then coated with acrylic acids, etc., and in the application force method, for example, a radical polymerization catalyst is usually added to an emulsion made by emulsifying an aqueous solution or a surfactant of acrylic acids, a crosslinking agent, and an ethylenically unsaturated compound. is added, impregnated into the foam, and then polymerized by heating at 40 to 1200 G for 1 to 10 hours to coat the acrylic acid copolymer on the pore walls of the foam.

The monomer concentration of the aqueous solution or emulsion is 2 to 30% by weight, and the foam is impregnated with 20 to 100% by weight of the monomer aqueous solution or emulsion.

Examples of radical polymerization catalysts include hydrogen peroxide, persulfates, benzoyl peroxide, abbisisobutyronitrile, and the like.

It is also possible to use a so-called redox system in combination with a reducing agent such as ferrous sulfate, sulfite, and ascorbic acid.

The amount of catalyst used is usually 0.1 to 3% by weight, preferably 0.2 to 2% by weight based on the monomer.

In addition, when coating the pore walls of a rubber foam with an acrylic acid copolymer, the foam is impregnated with a mixed solution of a copolymer of acrylic acids and an ethylenically unsaturated compound and a crosslinking agent, and crosslinked. It can also be obtained by

The copolymer is preferably water-soluble, with a content of 0.1 to 5
5 to 100% by weight of the crosslinking agent to the copolymer,
Preferably, the rubber foam is impregnated with 50 to 200% by weight of a mixed solution of 10 to 50% by weight, and 80 to 120'
By heating at C for 1 to 10 hours, the acrylic acid copolymer firmly coats the pore walls of the rubber foam, resulting in a hydrophilic foam with excellent durability.

In this case, it is preferable to use a bifunctional compound that reacts with the carboxyl group of acrylic acids as the crosslinking agent.
It is particularly preferable to use diglycidyl ethers in terms of durability and ease of crosslinking treatment.

When adding fibroin to the coating component, fibroin may be mixed as a powder or an aqueous solution into an aqueous solution or emulsion of acrylic acids, etc. or acrylic acid copolymers, etc., and the amount added is 1 to 10% based on the foam. It is preferable to adjust the amount to % by weight.

Next, the foam whose pore walls are coated with the acrylic acid copolymer is thoroughly washed with water and dried to obtain a hydrophilic foam.

The foam of the present invention has high hydrophilicity, with a hydrophilicity of 50 to 1,000
%, preferably 100-800%.

Here, the water absorption rate is determined by gently immersing a foam cut into a rectangular parallelepiped of 5 cm in size in 100 cc of water and measuring the weight increase after leaving it for 30 minutes.

That is, water absorption % The foam of the present invention has a high water absorption rate as well as a high water absorption rate.

For example, it is also excellent in diffusing water from the surface of the foam into the interior of the foam or absorbing water.

When 3m/ml of water is dropped onto the surface of a foam, it usually diffuses into the interior within 10 minutes.

Furthermore, the foam of the present invention has durable hydrophilic properties, is flexible even when dry, and has improved oil resistance, so it can be applied to various uses.

Examples include cosmetic foundation sponges, eye shadow brushes, water absorption rollers, ink rollers, and air diffusers.

The bulk density (apparent specific gravity) of the foam of the present invention is usually 0.05 to
0. 3 5. 9/cm is preferable, and can be appropriately selected depending on the application.

The present invention will be specifically explained below with reference to Examples.

The fibroin powder and foam used in the Examples were manufactured by the following method.

1. Method for producing fibroin powder 1 kg of raw silk was impregnated in 30A of a 1% by weight aqueous solution of Marcel soap, treated at 98° C. for 3 hours to remove sericin, and washed with water and dried.

The above-mentioned scouring raw silk was added in an aqueous solution of 3k9 containing 40% by weight of calcium nitrate and 20% by weight of ethyl alcohol. 5 kg
was added and dissolved at 75 to 80°C for 1 hour.

Next, 3klli+ of 80°C hot water was added to dilute and cool the mixture, which was then placed in a cellulose dialysis tube and desalted by dialysis in running water for 24 hours.

To 7 kg of the resulting 6.5% by weight aqueous fibroin solution was added 1k9 ethyl alcohol to gel the entire solution, which was then centrifuged and dried.

Next, it was ground with a jet mill to obtain 4kl of fibroin powder with a particle size of less than 3oμ. I got it.

2. Manufacturing method of foam (1) Nitrile butadiene rubber foam (Foam NB) Commercially available nitrile butadiene rubber emulsion bleach (Nipol LX531B, Nippon Zeon Co., Ltd.) 500.9, 15% by weight of colloidal sulfur, 20% by weight of zinc oxide, and mercapto. After adding 40 g of an aqueous dispersion containing 7% by weight of zinc benzothiazole and 7% by weight of zinc diethyldithiocarbamate, stirring and foaming the mixture to a volume of 1,000 to 4,000 cm to homogenize the bubbles. , sodium silicofluoride 25
25 g of a wt % aqueous dispersion was added and mixed.

Next, the foaming liquid was poured into a mold such as an oval aluminum pipe with a major axis of 12 cfI1 and a minor axis of 6 cm, and left to stand at room temperature.

Gelled foam 1 in an atmosphere of saturated steam at 105°C
After heating for an hour, remove from the container and wash thoroughly with water.
It was dried under a reduced pressure of 1 mmHg at °C for 5 hours, and then cut into appropriate pieces to prepare samples.

(2) 2-IJ fibroin rubber-fibroin foam (foam NF) An aqueous dispersion of 25% by weight fibroin powder in a nitrile-butadiene rubber emulsion was added (15.9% by weight).
A foam was produced by the operation 1).

(3) Natural rubber foam (foam NR) Using commercially available natural rubber latex (solid content concentration 60% by weight) in place of the nitrile butadiene rubber emulsion,
Except for adding 6g of surfactant potassium oleate (
A foam was produced by the operation 1).

Example 1 Bulk density 0.12-0. Each foam of 13 V has a major axis of 11.5 an and a minor axis of 5. Cut into pieces of 5 cm and 1.5 cm thick, prepare a solution having the composition listed in Table 1, impregnate the sample with the solution in the pick-up amount listed in Table 1, and heat at 105°C.
After heat treatment for 5 hours, the sample was washed with water and dried.

The physical properties of the foams produced according to the above formulation are shown in Tables 2 and 3. All the foams obtained by the method of the present invention are flexible even when dry, have highly durable hydrophilic properties, and have good mechanical properties. There was no deterioration.

Example 2 Bulk density 0.1-0.3g 1b each foam 5x5x3c
The pieces were cut into pieces with a size of m, impregnated with acnolic acids according to the formulation shown in Table 4, heated at 80°C for 5 to 8 hours, thoroughly washed with water, and dried.

As shown in Tables 5 and 6, the foam obtained by the method of the present invention has excellent durability and hydrophilicity, and also exhibits a remarkable effect on oil resistance.

Example 3 Bulk density: 0.13.9/cm Major axis: 1 1. According to the recipe of Experiment 41 3, 1 4 of Example 1 and Experiment A624 of Example 2. 5 Crn1 minor axis 5. 5 cm1 thickness 1.
A sensory test method in which each foam of 5an was subjected to hydrophilic treatment and the feel of cosmetics was tested on aqueous foundation cakes and powder type foundation cakes using commercially available polyvinyl alcohol sponges and natural rubber sponge cosmetic puffs as controls. ! i Female 18-32 years old 20
The preferred level of each item is scored by the person on a 5-point scale, and a total score of 85 or more is ◎ (very good), 70-8
4 points: ○ (good), 55 to 69 points: △ (slightly poor), 5
A score of 4 or less was evaluated as × (poor).

As shown in Table 7, commercially available natural rubber-based foundation cakes have poor compatibility with cosmetics because they lack hydrophilic properties, and were unfavorable in all evaluation items.

In addition, polyvinyl alcohol-based materials can provide a preferable feel when used completely in an iced state, but if left in an icy state for even one hour, water evaporates from the surface and the product becomes hard, resulting in an unfavorable feeling when used.

In the case of powder-type foundation cakes, polyvinyl alcohol-based products cannot be practically used because water is not used.

On the other hand, all of the foams according to the present invention are highly hydrophilic, flexible even when dry, and have excellent water retention properties, so they have excellent usability in both water-based and powder types. .

For water-based foundation cake, use a damp sponge.

The values in parentheses indicate the feeling of use after being left in an atmosphere of 35°C and 40% RH for 1 hour after containing 150% water by weight.

Powder type foundations are used dry.

Evaluation item A: How well the cosmetics transfer to the sponge.

B. Skin texture when applied to face C. How the cosmetic spreads on the skin and the finish.

Claims (1)

[Scope of Claims] 1. The pore walls of the rubber foam are 0% relative to the rubber foam.
．． 2 to 15% by weight of acrylic acids (4) represented by the following general formula, crosslinking agent (B) and ethylenically unsaturated compound (C
A hydrophilic foam coated with an acrylic acid copolymer obtained by polymerizing ). (4) CH2-CR1COOM [wherein R1 represents hydrogen or a methyl group, and M represents hydrogen, an alkali metal or ammonium. ] (B) May be different. ](O CH2-CR3Z [However, in the formula, R3 represents hydrogen or a methyl group, and Z represents an organic residue.]2. The rubber foam according to claim 1, wherein the rubber foam is natural rubber or nitrile butadiene rubber. Foam.3 The acrylic copolymer contains 50-80% by weight of acrylic acids (A), 5-30% by weight of crosslinking agent (B) and at most 30% by weight of acrylic acids (A).
2. A foam according to claim 1, which is a copolymer of ethylenically unsaturated compounds in an amount of % by weight. 4 The pore walls of the rubber foam are 0.
The foam according to claim 1, which is coated with 5 to 7% by weight of an acrylic acid copolymer. 5. The foam according to claim 1, wherein the rubber foam contains 0.5 to 5% by weight of fibroin. 6 Rubber foam containing acrylic acids (4), crosslinking agent (B) and ethylenically unsaturated compound (
A method for producing a hydrophilic foam, which comprises applying a solution containing C) and then copolymerizing it. (A) CH2=CR, COOM (However, R1 and M are the same as above) (B) X-R2-Y (However, in the formula, X, Y and R2 are the same as above) (C) CH2
-CR3Z (wherein R3 and Z are the same as above) 7. The method for producing a foam according to claim 6, wherein the copolymerization is carried out in the presence of a radical polymerization catalyst. 8 Claim 6 in which the copolymerization is carried out at 40 to 120°C
Method for manufacturing the foam described in Section 1. 9. The method for producing a foam according to claim 6, wherein the crosslinking agent (9) is a diacrylate. 10. A method for producing a foam, which comprises applying a solution containing an acrylic acid (a copolymer of A and an ethylenically unsaturated compound ma, and a crosslinking compound IXB) to a rubber foam, and then subjecting the foam to a crosslinking reaction. (A) CH2-CR1COOM (However, in the formula, R1 and M are the same as above) (B) X-R2-Y (However, in the formula, X, Y and R2 are the same as above) (C) CH2
-CR3Z (However, R3 and Z in the formula are the same as above.) 11. The method for producing a foam according to claim 10, wherein the crosslinking reaction is carried out at 80 to 120°C. 12. The method for producing a foam according to claim 10, wherein the crosslinking agent (B) is a diglycidyl ether.