JP3202948B2 - Latex and latex sponge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic rubber latex composition and a cosmetic or cleaning latex sponge using the same as a raw material. More specifically, the present invention relates to a latex sponge raw material having a low viscosity at a high concentration. The latex sponge using the synthetic rubber latex composition has reduced metal ion contamination, and the compounded antibacterial agent remains. It's about a sponge that is.

[0002]

2. Description of the Related Art Sponge made from rubber latex is used for cosmetic puffs, squeezing rolls for washing, bath sponges and the like. However, latex sponge is made of copper,
It is known that sponges are discolored by encountering heavy metal ions such as silver and chromium. For cosmetic and cleaning sponge applications, it is contaminated with metal ions contained in trace amounts of water used for cleaning, especially copper ions eluted from hot water supply equipment and copper and silver ions from antibacterial tools, and turns brown. . This gives an appearance as if dirt has adhered, giving the illusion that dirt has not yet fallen off, or mistaking it as true dirt. Further, discoloration also occurs due to direct contact with copper alloys such as metallic copper, gunmetal, brass, phosphor bronze and the like. This means that a specific sulfur compound to be compounded in the rubber combines with a metal ion to exhibit a specific coloration.

On the other hand, Japanese Patent Application Laid-Open No. 61-48308 discloses
In the invention described in Japanese Patent Application Laid-Open Publication No. H11-157, it is proposed that a cosmetic puff is subjected to an antifouling treatment by immersion treatment in an oxidized bleaching agent. This antifouling treatment oxidizes and decomposes sulfur compounds. In the invention described in JP-A-63-234401, it is stated that a sponge with less contamination was obtained by vulcanizing at a high temperature for a long time using an accelerator blending without using an accelerator EZ.
This is because metal ion contamination is caused by EZ mixed in the latex sponge.
On the other hand, the invention described in Japanese Patent Application Laid-Open No. 50-141642 is a method for producing a latex for a sponge. After the polymerization reaction, a polymerization terminator and a monomer are added, and the mixture is stirred to enlarge the latex particles. It is said to be manufactured by removal and concentration. According to this method, a rubber latex having a low viscosity at a high concentration suitable for a latex sponge and having a low gel content can be obtained.

[0004]

According to the above-mentioned method, although the effect of reducing contamination is sufficient, there is a problem that various chemicals added to the sponge together with the sulfur compound are oxidatively decomposed. Examples of the chemical include an antibacterial agent added for preventing rot and mold, and there is a problem that its effect is completely lost after antifouling processing.
For this reason, the compounding amount is made extremely excessive in advance so that an effective amount remains after processing, or a measure such as impregnating with a chemical after antifouling processing is employed, thereby wasting material and complicating the process. Has occurred. Further, according to the above method, when a sponge is prepared by using a composition not using the accelerator EZ, the metal ion contamination property is remarkably improved as compared with the case where EZ is used, but the contamination property still remains. It is inferior to sponge subjected to antifouling treatment with a bleaching agent, and cannot be said to have a sufficient effect of reducing contamination. Further, there is also a problem that the sponge has a yellowish dull color due to the high temperature and long time vulcanization, and a white sponge cannot be produced or cannot be freely colored. In addition, this vulcanization operation requires a high-pressure steam vulcanizer, which is disadvantageous in terms of equipment. Sponge made from the latex of the other method has metal ion contamination. In addition, latex alone has metal ion contamination.

Accordingly, the present invention provides a latex sponge having reduced metal ion contamination and a raw material latex thereof, which does not require a high-pressure steam vulcanizer or an antifouling process and can be produced by a conventional production apparatus. Another object of the present invention is to provide a latex sponge in which metal ion contamination is reduced and a blended antibacterial agent remains, to solve the above-mentioned problems.

[0006]

In the present invention, as a result of intensive studies to solve the above-mentioned problems, latex sponge raw latex itself has metal ion contamination, and latex sponge using this as a raw material is also required. It was found that there was metal ion contamination, and the metal ion contamination of the raw latex could be significantly improved by adding a radical polymerization initiator to this latex. It was found that the properties were remarkably improved, and that agents such as antibacterial agents incorporated with a beautiful appearance remained sufficiently. In the present invention, the reason why the radical polymerization initiator is added to the latex and the metal ion contamination of the latex itself is remarkably improved is that the polymerization terminator added during the particle enlargement operation in the latex production before the modification is a metal terminator. It is a cause of ion contamination, and it is presumed that metal ions are not contaminated by radical scavenging.

That is, according to the first aspect of the present invention, the polymerization reaction is stopped, the organic solvent is removed, and a polymerization terminator is contained.
A radical polymerization initiator is added to a rubber latex having a viscosity of 1000 centipoise or less at a concentration of 0%,
By reacting with the above-mentioned polymerization terminator at the following temperature, a latex composition having reduced metal ion contamination was obtained. Claim 2
The invention according to claim 1 is to add a rubber compounding agent such as a crosslinking agent and an accelerator to the latex composition according to claim 1 to foam, gel,
A latex sponge obtained by vulcanization was obtained.

[0008]

Embodiments of the present invention will be described below. Examples of the latex before the modification include a synthetic rubber latex, and a rubber latex such as styrene butadiene rubber, butadiene rubber, IR, CR, and nitrile butadiene rubber. These can be used alone or in combination of two or more. For sponge applications, high concentration and low viscosity are required,
It is preferable that the viscosity at a concentration of 70% is 1000 centipoise or less. Such a latex is obtained by enlarging latex particles. When the latex reaches a predetermined conversion during the polymerization reaction, the polymerization reaction is stopped by adding a polymerization terminator, and then a solvent that dissolves or swells the produced polymer is added to enlarge the particles.

As the polymerization terminator, dithiocarbamates are preferred in view of the low generation of gel components. Examples thereof include sodium and ammonium salts of dimethyldithiocarbamic acid, and sodium and ammonium salts of diethyldithiocarbamic acid. Can be As the solvent, various solvents in which the produced polymer dissolves or swells can be used, but it is preferable to use a raw material monomer in terms of reusing the removed solvent. The polymerization terminator is used to stop the polymerization reaction of the solvent monomer together with the purpose of terminating the polymerization reaction of the latex. The amount of the polymerization terminator is 0.1 to 10 parts by weight per 100 parts by weight of the solid content of the produced latex.
Parts by weight. The viscosity of the latex can be reduced by enlarging the particles while stirring, and the viscosity at a concentration of 70% is preferably from 200 to 1000 centipoise. When the particle size reaches the specified value, the solvent is removed and the concentration is adjusted to a specified value.
A raw latex for latex sponge is obtained. This latex has metal ion contamination, and becomes brown when an aqueous solution of copper sulfate having a copper ion concentration of 100 ppm is dropped into the latex.

Examples of the radical polymerization initiator include inorganic radical polymerization initiators such as peroxides, peroxide salts, perchlorates, periodates, perbromates, perboric acids and salts thereof. used. Organic peroxides, azo compounds and the like are used, and among them, water-soluble ones are easy to use and effective. Examples of this include hydrogen peroxide, sodium persulfate,
Sodium percarbonate is preferred. As organic peroxides,
Benzoyl peroxide p, p 'disulfonyl sodium, and azo compounds include 2,2-azobis- (2-
Aminodipropane) dihydrochloride and the like. These polymerization initiators can be used in combination with a reducing agent, and examples of the reducing agent include sodium pyrobisulfite, sodium hydrogen sulfite, ferrous sulfate, and sodium L-ascorbate. The amount of addition of this radical polymerization initiator is 10% of solid content of latex.
It is 0.01 part by weight to 5.0 parts by weight based on 0 part by weight. If it is less than this, the metal ion contamination cannot be reduced, and if it is more than this, the stability of the latex is impaired.

The radical polymerization initiator is added to the latex as an aqueous solution. The concentration of the aqueous solution is preferably high in a range that does not cause coagulation in the latex in order to keep the latex concentration high. The addition is preferably carried out while stirring the latex, since coagulation is not generated in the latex. When the mixture is uniformly mixed, the stirring may be stopped. The processing temperature is from 0 ° C. to 70 ° C. If the temperature is lower than this, there is a risk of freezing of the latex, and if the temperature is higher than 70 ° C., a coagulated product is generated, which is not preferable. The reaction starts from the time of addition and almost reaches the end after 2 hours.

[0012] The metal ion contamination can be determined by contacting the latex dropwise with an aqueous solution of copper sulfate having a copper ion concentration of 100 ppm, so that the brown color remains white.
It can be seen that the metal ion contamination was reduced. After this, it takes more time to decompose the unreacted radical polymerization initiator. Alternatively, the unreacted radical polymerization initiator is decomposed by an operation such as raising the temperature, adding a reducing agent, or adding a peroxide-decomposing enzyme. If the radical polymerization initiator remains, the sulfur crosslinking reaction during rubber production is inhibited. The latex of the present invention may contain a surfactant and a stabilizer for adjusting the pH as needed. Thus, the latex of the present invention is obtained.

The above operation can be carried out by mixing two or more kinds of latex before modification, and also by mixing two or more kinds of latex before modification with latex having no metal ion contamination. it can. The latex of the present invention can subsequently be used in the production of sponges described below,
It can be stored in a storage tank or the like and used for sponge production as required.

The latex sponge of the present invention is obtained by foaming the latex of the present invention. As a method of producing a sponge, a sponge having rubber elasticity is obtained by mixing air into a latex composition obtained by adding at least a crosslinking agent, a rubber compounding agent and a gelling agent to a raw material latex, foaming by stirring, and vulcanizing. can get. Raw material latex is the above-mentioned treated latex of the present invention,
If necessary, natural rubber latex, latex before treatment, synthetic resin emulsion, water-soluble resin and the like can be mixed. Crosslinking agents include sulfur.

Examples of the accelerator include thiazoles, sulfenamides, thioureas, guanidines, amines,
Xanthogenic acids can be used, and one or more of these can be used as a mixture, and the amount used is 0.5 to 5.0 parts by weight per 100 parts by weight of the solid content of the latex. Is appropriately selected depending on the physical properties of the sponge. Among these, preferred examples include MZ (zinc salt of 2-mercaptobenzothiazole), DM (2-benzothiazolyl disulfide), sodium salt of 2-mercaptobenzothiazole, diethylthiourea, H (hexamethylenetetramine), Xanthogen sulfide (eg, diethyl or dipropyl or dibutyl xanthogen sulfide), xanthogen disulfide (eg, diethyl or dipropyl or dibutyl xanthogen disulfide) and the like can be mentioned. Among these, xanthogen sulfide and xanthogen disulfide have very little metal ion contamination, have good physical properties of a crosslinked product, and give a white sponge. The amount of xanthogen sulfide and xanthogen disulfide to be used ranges from 0.05 to 5.0 parts by weight per 100 parts by weight of latex solids.
0 parts by weight can be used in combination with the other accelerators described above, or 0.5 to 5.0 parts by weight can be used alone. In order to activate the above accelerator, one or more of dithiocarbamic acids and thiurams may be used in combination.

Examples of the gelling agent include one or more of metal oxides, inorganic salts, acids, salts of organic acids, etc. Among them, zinc oxide, aluminum sulfate, sodium silicofluoride and ammonium acetate are preferred. . The foamed latex composition mixed with a gelling agent is gelled by a method such as chemically gelling or thermally gelling. In addition, a gelling modifier can be used in combination. Examples of the gelling modifier include trimen base (trade name, manufactured by Uniroyal), a reaction product of ethyl chloride, formaldehyde and ammonia, alkylamines, nonionic stone Ken and the like.

The latex sponge of the present invention may contain an antibacterial agent in addition to the above. The antibacterial agent can be appropriately selected from various types, but from the viewpoints of sustained effect and safety for the human body, zinc-based antibacterial agents such as bis (2-pyridylthio-1-oxide) zinc and 2- (4-thiazolyl)-
Organic antibacterial agents such as benzimidazole are preferred, and one or more of them can be mixed and compounded. The amount is resin 1
It is preferable to add 0.01 to 2.0 parts by weight per 00 parts by weight. If the amount is less than this, there is no antibacterial effect, and if it is more than this, the foam of the sponge becomes coarse. The latex sponge of the present invention may further contain an antioxidant, a metal deactivator, an ultraviolet absorber, a lubricant, a plasticizer, a filler, a colorant, a flame retardant, and a fragrance in addition to a rubber compounding agent, if necessary. Can be blended.

The foaming is carried out by mixing air with a latex composition containing the above-mentioned composition and stirring the mixture. Examples of the vulcanization include steam vulcanization and hot air vulcanization. The vulcanization temperature is from 80 ° C to 150 ° C. Of these, performing steam vulcanization at a vulcanization temperature of 110 ° C. or less is preferable in that a white sponge can be obtained. In addition to this, 10
Performing steam vulcanization at 0 ° C. or less is more preferable because a high-pressure steam vulcanizer is not required. The sponge of the present invention is washed and dried as necessary, and finished in a shape suitable for the intended use. According to the present invention, it can be applied to the removal of thiuram added to natural rubber latex, and can also be applied to latex rubber products in which nitrosamine-forming substances are reduced.

Example 1 NBR latex for latex sponge (Nippol LX531B manufactured by Zeon Corporation, solid content 66%) was 70%.
%, Has a viscosity of 400 centipoise, contains a polymerization terminator sodium dimethyldithiocarbamate, and has metal ion contamination. This latex 10
While weighing 0 kg, 1 kg of a 3.5% aqueous solution of hydrogen peroxide as a radical polymerization initiator was added and mixed over 2 minutes while stirring with a rotary blade type stirrer. The liquid temperature at this time was 20 ° C. Thereafter, stirring was stopped and the mixture was left for 1 hour. When an aqueous solution of copper sulfate having a copper ion concentration of 100 ppm was contacted dropwise, the raw material latex showed a brown color,
Not shown after above treatment. After that, it was left for 48 hours.
The above viscosity is a value of a B-type viscometer rotor rotation speed of 60 rpm at 25 ° C.

Example 2 Per 100 parts by weight of resin solid content of the latex treated in Example 1 Example 2 1.5 sulfur, 0.5 trimene base, 2.0 MZ, 1.0 antioxidant, 0.2 antibacterial, Example 3 Zinc oxide 2.0, sodium silicofluoride 3.0 (parts by weight of non-volatile content, the same applies hereinafter) Example 3 1.5 sulfur, 0.5 trimen base, 1.0 MZ, 1.0 diisopropylxanthogen disulfide, 1.0 anti-aging Agent 1.0, antimicrobial agent 0.2, zinc oxide 2.0, and sodium silicofluoride 3.0 were respectively mixed, and air-mixed with an Oaks mixer to foam to an expansion ratio of 8.6. After gelation, steam vulcanization was performed at 100 ° C. for 50 minutes. Washing with water,
It was dehydrated, cut to a thickness of 8 mm, and dried to obtain a latex sponge exhibiting rubber elasticity.

In the above examples, trimen base is a reaction product of ethyl chloride, formaldehyde and ammonia (trade name, manufactured by Uniroyal), and MZ is 2
A zinc salt of mercaptobenzothiazole, an antioxidant 2,6-di-tert-butyl-4-methylphenol, and an antibacterial agent bis (2-pyridylthio-1-oxide)
Zinc.

Comparative Example 1 A latex sponge was obtained in the same manner as in Example 2 except that the unmodified latex of Example 1 was used. Comparative Example 2 In the same manner as in Comparative Example 1, steam vulcanization was performed at 115 ° C. for 60 minutes. Comparative Example 3 Further, Comparative Example 1 was immersed in a 0.5% aqueous solution of sodium perborate at 80 ° C. for 30 minutes, and then dehydrated, washed with water, dehydrated and dried to obtain an antifouling latex sponge.

[0023]

[Table 1]

In Table 1 above, the metal ion contamination was determined by impregnating a sponge with an aqueous solution of copper sulfate having a copper ion concentration of 50 ppm, washing with water and drying, and measuring the color difference from the sponge before impregnation. Color difference dE * 3: less than 3, excellent: 3 or more and less than 12, good: 12 or more. The residual ratio of the antibacterial agent was analyzed by thin layer chromatography after elution of the solvent. Regarding the antibacterial property, it was measured in a compulsory contamination test of JIS Z 2911.
゜ C: Cultured for 14 days, those with mold development within 7 days are poor, those with mold development within 10 days are acceptable, those with mold development within 14 days are good, Those which did not develop mold within 14 days were regarded as excellent. The whiteness is a degree of whiteness according to ASTM E 313. Excellent is 40 or more, good is 30 or less and good is 30 or less, and color tone is less than 30. The tensile strength and elongation are values at break according to JIS K 6301, and the unit is [kgf / cm ² ]. Wear resistance is JI
Sample width 10 mm, load 2 using a friction tester type 2 of SL 0823
The sample was rubbed 500 times at 00 g, and the abrasion loss was measured.
Excellent wear loss of 0 mg or more and less than 5 mg, 5 mg or more and 10
Less than mg is good, 10mg or more and less than 20mg are acceptable, 20m
g or more was not allowed.

The sponges of Examples 2 and 3 produced from Example 1 are sponges excellent in rubber elasticity and having a good touch like the sponges of Comparative Example 1 produced from unmodified latex, and are suitable for cosmetics. It was excellent. These are excellent in reduction of metal ion contamination, and the compounded antibacterial agent remains, and is excellent in antibacterial properties. On the other hand, the sponge of Comparative Example 1 produced from the unmodified latex had metal ion contamination. Although this staining property was improved by performing high-temperature and long-time vulcanization in Comparative Example 2, the sponge had a dull yellow color, had poor whiteness, and had poor sponge properties. Further, the metal ion contamination was remarkably improved by the antifouling treatment of Comparative Example 3, but at the same time, the antibacterial agent disappeared, the antibacterial effect was remarkably poor, and the sponge properties were also poor.

[0026]

According to the first aspect of the present invention, the raw latex produced by allowing a radical polymerization initiator to act on the raw latex has significantly reduced metal ion contamination.

According to a second aspect of the present invention, there is provided a latex sponge produced by using the raw material latex according to the first aspect of the present invention. As in the first aspect, metal ion contamination is significantly reduced.

[0028]

[0029]

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 9/00-21/02 C08J 9/00-9/42 C08K 3/00-13/08 CA (STN ) WPI / L (DIALOG)

Claims (2)

(57) [Claims] The polymerization reaction is terminated, the organic solvent is removed, and a radical polymerization initiator is added to a rubber latex containing a polymerization terminator and having a viscosity of not more than 1,000 centipoise at a concentration of 70%. A latex composition characterized by reacting with the above-mentioned polymerization terminator at a temperature of not more than ℃ to reduce metal ion contamination. 2. A radical polymerization initiator is added to a rubber latex having a viscosity of 1,000 centipoise or less at a concentration of 70% containing a polymerization terminator, terminating the polymerization reaction, removing an organic solvent, and adding a polymerization terminator. A latex sponge produced by reacting with the above-mentioned polymerization terminator at a temperature of not more than ° C and using a latex composition having reduced metal ion contamination as a raw material.