Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/02—Direct processing of dispersions, e.g. latex, to articles
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
  • C08C1/00—Treatment of rubber latex
  • C08C1/02—Chemical or physical treatment of rubber latex before or during concentration
  • C08C1/04—Purifying; Deproteinising
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
  • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
  • C12N9/14—Hydrolases (3)
  • C12N9/48—Hydrolases (3) acting on peptide bonds (3.4)
  • C12N9/50—Proteinases, e.g. Endopeptidases (3.4.21-3.4.25)
  • C12N9/52—Proteinases, e.g. Endopeptidases (3.4.21-3.4.25) derived from bacteria or Archaea
  • C12N9/54—Proteinases, e.g. Endopeptidases (3.4.21-3.4.25) derived from bacteria or Archaea bacteria being Bacillus
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
  • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
  • C12N9/96—Stabilising an enzyme by forming an adduct or a composition; Forming enzyme conjugates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2307/00—Characterised by the use of natural rubber

Definitions

• the present invention relates to a deproteinizing agent for removing a protein in a natural rubber, a deproteinized natural rubber latex obtained by using the same, and a method of producing a rubber product using the rubber latex.
• Natural rubbers have widely been used in various fields, for example, industrial goods such as automobile tire, belt and adhesive, household goods such as glove, medical appliances such as catheter, lactation appliances, contraceptive device and the like because of features such as large extension, high elasticity and strong film strength.
• glove, medical appliances and lactation appliances are products obtained by dipping a mold for these rubber products in a natural rubber latex and these dipped products are produced by using (a) a so-called direct method of directly dipping a mold in a natural rubber latex, (b) a so-called anode coagulation method of coating a mold with an anode coagulant and dipping the mold in a natural rubber latex, and (c) a so-called heat sensitizing method of dipping a previously heated mold in a natural rubber latex containing a heat sensitizer, thereby gradually depositing a gel on the surface of the mold.
• These preparation methods are appropriately selected according to the kind of dipped products.
• the direct method is employed when producing products such as condom made of a rubber film having a very small thickness
• the anode coagulation method is employed when producing a household glove made of a rubber film having a thickness of about 1 mm
• the heat sensitizing method is employed when producing more thick products such as work glove.
• immediate allergy which shows symptoms such as respiratory distress and anaphylactoid symptom (e.g. vascular edema, urttication, collapse, cyanosis, etc.) within several hours. It is presumedthat such immediate allergy is causedby a protein, as an antigen, in the natural rubber.
• the protein contained in the natural rubber causes variations in quality and vulcanization properties of the natural rubber because the kind and quantity of the protein vary depending on the locality and production season of the natural rubber latex.
• the protein can cause deterioration of mechanical characteristics such as creep characteristics and aging resistance and electrical characteristics such as insulating properties.
• Japanese Published Unexamined Patent Korean Published Unexamined Patent (Kokai Tokkyo Koho Hei) No. 6-56902 discloses a method of adding a proteolytic enzyme (protease) and a surfactant to a natural rubber latex, thereby decomposing a protein, and separating a creamy deproteinized natural rubber component by centrifugation.
• proteolytic enzyme proteolytic enzyme
• surfactant surfactant
• the protein in the natural rubber latex can be removed in a very high level and the nitrogen content (N%) is reduced to 0.1% by weight or less as measured by the Kjeldahl method.
• the direct method of directly dipping the mold in the natural rubber latex to form a film causes liquid dripping, thereby making it difficult to form a uniform thin film. Namely, it is difficult to produce a dipped product having a very small film thickness, such as condom, in a uniform film thickness by using the deproteinized natural rubber latex.
• the deproteinized natural rubber latex obtained by the method described above has a problem that coagulation of rubber particles can not be effected by a conventional heat sensitizer, thereby making it impossible to form a film according to the formulation of a conventionally used heat sensitizing method.
• the method described in the publication described above has a problem that, since the both of the heat sensitizer and anode coagulant are incorporated into the latex, the latex becomes unstable as compared with a conventional heat sensitizing method using a natural rubber latex, thereby making it impossible to obtain long-term stability and making it hard to control heat-sensitive properties.
• a dip product having a sufficient film thickness is obtained by using a specific heat sensitizer and a specific anode coagulant in a specific combination and incorporating the specific combination into a deproteinized natural rubber latex wherein rubber particles are excessively stabilized, obtained by the method described above, in a large amount as compared with a conventional formulation (Japanese Published Unexamined Patent (Kokai Tokkyo Koho) No. 2000-17002).
• an object of the present invention is to provide a deproteinizing agent which can realize high deproteinization of a natural rubber latex and provide the latex with sufficient heat-sensitive coagulation properties while maintaining the stability of the deproteinized natural rubber latex for a long term, and to provide a method of preparing a deproteinized natural rubber latex which simultaneously satisfy the stability and heat-sensitive coagulation properties of the latex.
• Another object of the present invention is to provide a method capable of producing a uniform dipped product having a very small film thickness from a highly deproteinized natural rubber latex, as a raw material, without causing liquid dripping.
• a still another object of the present invention is to provide a method capable of producing a dipped product having a sufficient film thickness from a highly deproteinized natural rubber latex, as a raw material, even in case of the same formulation as that of a conventional heat-sensitive latex using a natural rubber latex, the method capable of easily controlling the heat-sensitive properties.
• the present inventors have intensively studied to solve the problems described above and found such a novel finding that, when a deproteinization treatment is conducted by incorporating a predetermined water-soluble polymer, together with a protease used conventionally in a deproteinization treatment of a natural rubber latex, there can be obtained a natural rubber latex deproteinized highly by the treatment and such a latex shows sufficient heat-sensitive coagulation properties while maintaining the long-term stability.
• the present invention has been completed.
• the deproteinizing agent for natural rubber latex according to the present invention is characterized in that it comprises a protease and one or more water-soluble polymers as an active component.
• the deproteinizing agent of the present invention regardless of its simple constitution as described above, it is made possible to highly deproteinize a protein in a natural rubber latex, to maintain the stability of the deproteinized natural rubber latex for a long term, and to provide the deproteinized natural rubber latex with sufficient heat-sensitive coagulation properties.
• the water-soluble polymer in the deproteinizing agent of the present invention is a polymer having at least one hydrophilic functional group selected from a hydroxyl group, a carboxyl group, an amide group and an ester bond, or a salt thereof, a principal chain of the polymer having 100 to 5,000,000 carbon atoms.
• polymer described above makes it possible to simultaneously provide the deproteinized natural rubber latex with the long-term stability and sufficient heat-sensitive coagulation properties.
• the polymers may be used alone or in combination.
• a weight ratio of the protease to the water-soluble polymer is preferably within a range from 1:1 to 1:200.
• the deproteinized natural rubber latex of the present invention is characterized in that it is prepared by subjecting to a deprotenization treatment using the deproteinizing agent of the present invention.
• the method of producing a deproteinized natural rubber latex according to the present invention is characterized in that it comprises adding the deproteinizing agent of the present invention to a natural rubber latex, thereby maturing the natural rubber latex, and washing rubber particles in the latex.
• the deproteinized natural rubber latex obtained by the method of the present invention is a stable latex, a protein of which is highly removed. Because of its sufficient heat sensitivity, the latex is suited for use as a raw material for producing thick rubber products such as work glove, catheter and the like.
• the amount of the deproteinizing agent is preferably within a range from 0.001 to 10 parts by weight based on 100 parts by weight of the rubber solid content in the natural rubber latex.
• the present inventors have studied about the method of producing the rubber product using the natural rubber latex deproteinized by the deproteinizing agent described above and succeeded in obtaining rubber products having good quality, industrially advantageously, by the following methods (1) and (2).
• a dipped product made of a film which has a very small thickness and uniform, can be produced by incorporating a conventionally known vulcanizing agent into the deproteinized natural rubber latex in accordance with the same formulation as in case of a normal compound latex, using the direct (dipping) method.
• a dipped product made of a film having a sufficient thickness can be produced by incorporating a conventionally known vulcanizing agent into the deproteinized natural rubber latex in accordance with the same formulation as in case of a normal heat-sensitive compound latex, using the heat sensitizing method.
• the method (1) of producing a rubber product using a deproteinized natural rubber latex according to the present invention is characterized in that it comprises adding a protease and one or more water-soluble polymers to a natural rubber latex, thereby subjecting the natural rubber latex to a deproteinization treatment, incorporating at least a vulcanizing agent into the latex, dipping a mold in the resulting compound latex, and vulcanizing and drying a rubber film formed on the mold.
• the method (2) of producing a rubber product using a deproteinized natural rubber latex according to the present invention is characterized in that it comprises adding a protease and one or more water-soluble polymers to a natural rubber latex, thereby subjecting the natural rubber latex to a deproteinization treatment, incorporating at least a heat sensitizer and a vulcanizing agent into the latex, dipping a mold in the resulting heat-sensitive coagulating compound latex, and vulcanizing and drying a rubber film formed on the mold.
• the protein can be highly removed from the natural rubber latex and, moreover, the dipped product made of a film, which has a very small thickness and uniform, can be produced easily by the direct (dipping) method regardless of use of the highly deproteinized natural rubber latex as the raw material.
• the protein can be highly removed from the natural rubber latex and, moreover, the dipped product made of a thick film can be produced easily by the heat sensitizing method regardless of use of the highly deproteinized natural rubber latex as the raw material.
• the deproteinized natural rubber product thus produced shows not only low allergy because of removal of the protein, but also excellent characteristics with respect to softness and extension. Furthermore, a thin and uniform rubber film can be produced by the direct dipping method and a comparatively thick rubber product can be produced by the heat sensitizing method.
• the heat sensitizer used in the method (2) is preferably a water-soluble polymer type heat sensitizer.
• the amount of the heat sensitizer is preferably adjusted within a range from 0.1 to 10 parts by weight based on 100 parts by weight of the rubber solid content in the deproteinized latex.
• the deproteinizing agent of the present invention contains a protease and one or more water-soluble polymers as an active component, as described above.
• the protease used in the deproteinizing agent of the present invention is not specifically limited and a conventionally known one can be used and, for example, an alkaline protease is preferable.
• the protease may be derived from any of bacteria, filamentous bacteria and yeast, and the protease is preferably derived from bacteria, particularly preferably from the genus Bacillus. It is also possible to use enzymes such as lipase, esterase, amylase, lacase and cellulase in combination.
• protease KAP having a resistance to the surfactant manufactured by Kao Corp. is used particularly preferably.
• the amount of the protease varies depending on the amount of the deproteinizing agent described below of the present invention and the activity of the protease itself, and is not specifically limited.
• the amount of the deproteinizing agent is adjusted so that the amount of the protease in the deproteinizing agent is preferably adjusted within a range from 0.0001 to 20 parts by weight, and more preferably within a range from 0.001 to 10 parts by weight, based on 100 parts by weight of the rubber component in the natural rubber latex.
• the amount of the protease is within the range described above, a protein in the latex can be sufficiently decomposed while maintaining the activity of the protease.
• the effect corresponding to the amount of the protease can be exerted effectively and, therefore, it is advantageous in view of the cost.
• More specific examples are those, wherein the principal chain has 100 to 5,000,000 carbon atoms, among (meth)acrylate polymer, alginate polymer, vinyl polymer, polyethylene oxide polymer and cellulose polymer.
• Examples of the (meth)acrylate polymer include sodium polyacrylate, sodium polymethacrylate, ammonium polyacrylate, and ammonium polymethacrylate.
• alginate polymer examples include sodium alginate, ammonium alginate, potassium alginate, and propylene glycol alginate.
• Examples of the vinyl polymer include polyvinyl alcohol (PVA), and a potassium salt (saponified substance) of PVA.
• polyethylene oxide polymer examples include polyethylene oxide and polypropylene oxide.
• Examples of the cellulose polymer include carboxymethylcellulose (CMC), hydroxyethylcellulose, hydroxypropylcellulose, and cellulose xanthogenate.
• CMC carboxymethylcellulose
• hydroxyethylcellulose hydroxyethylcellulose
• hydroxypropylcellulose hydroxypropylcellulose
• cellulose xanthogenate examples of the cellulose polymer
• the water-soluble polymer in the deproteinizing agent of the present invention is not limited to the polymers described above and there can be used protein-based water-soluble polymer (e.g. casein, etc.), sodium carboxymethylstarch, sodium starch phosphate or the like.
• a small amount of a surfactant can also be added to the deproteinizing agent of the present invention, together with the polymer described above.
• the content of the surfactant is large, the stability of the latex is excessive and the effect of the present invention is likely to be impaired. Accordingly, a sufficient consideration must be paid to the amount.
• polyoxyethylene nonionic surfactant As the stabilizer used in the deproteinization treatment to a conventional natural rubber latex, “polyoxyethylene nonionic surfactant” is known. However, since a hydrophobic group of such a surfactant is merely that obtained by bonding about several to thirty ethylene glycols, the polyoxyethylene nonionic surfactant is not included in the category of the water-soluble polymer in the present invention.
• the amount of the water-soluble polymer varies depending on the amount of the deproteinizing agent described below of the present invention and properties of the water-soluble polymer itself and is not specifically limited.
• the amount of the deproteinizing agent is generally adjusted so that the content of the water-soluble polymer is preferably within a range from 0.1 to 10 parts by weight, and more preferably within a range from 0.5 to 3 parts by weight, based on 100 parts by weight of the rubber content in the natural rubber latex.
• the content of the water-soluble polymer is within the range described above, it is made possible to simultaneously satisfy the stability and heat-sensitive coagulation properties of the deproteinized natural rubber latex.
• Ratio of protease to water-soluble polymer The protease and water-soluble polymer in the deproteinizing agent of the present invention are contained in a weight ratio within a range from 1:1 to 1:200, as described above.
• the ratio of the protease to the water-soluble polymer in the deproteinizing agent of the present invention is preferably within a range from 1:5 to 1:100, and more preferably within a range from 1:10 to 1:50, among the above range.
• the deproteinized natural rubber latex of the present invention is characterized in that it is prepared by subjecting to a deprotenization treatment using the deproteinizing agent of the present invention.
• the method of producing a deproteinized natural rubber latex according to the present invention is characterized in that it comprises adding the deproteinizing agent of the present invention to a natural rubber latex, thereby maturing the natural rubber latex, and cleaning rubber particles in the latex.
• the amount of the deproteinizing agent is decided by the content of the protease in the deproteinizing agent and the activity of the protease, and is usually set within a range from 0.0001 to 10 parts by weight, and preferably within a range from 0.001 to 10 parts by weight, based on 100 parts by weight of the rubber content in the latex.
• the amount of the deproteinizing agent is smaller than the above range, the deproteinizing effect becomes poor and it is likely to become impossible to sufficiently remove a fear of the occurrence of immediate allergy caused by the protein.
• the deproteinization treatment is conducted by adding a deproteinizing agent of the present invention to a natural rubber latex as the raw material, as described above, and maturing the latex for about several tens minutes to one week, more preferably about 1 to 3 days.
• a protein in the natural rubber latex can be decomposed.
• This maturing treatment may be conducted while stirring the latex or allowing it to stand.
• the temperature may be controlled and is controlled within a range from 5 to 90° C., and preferably from 20 to 60° C. to obtain sufficient activity of the enzyme.
• the temperature is lower than 5° C., there is a fear that the enzyme reaction does not proceed.
• the temperature exceeds 90° C., there is a fear that the enzyme is devitalized.
• the cleaning (purification) treatment of rubber particles in the latex after the deproteinization treatment includes, but is not specifically limited to, a treatment of concentrating the latex by centrifugation or ultrafiltration and separating the non-rubber component transferred in water such as protein decomposition product and the rubber particles in the latex, or a treatment of separating the rubber particles by cohesion using an acid.
• a sufficient deproteinizing effect can be obtained by dispersing a cream component separated in the upper layer by centrifugation under the conditions of 5,000 to 15,000 rpm for about 1 to 60 minutes (or gravity acceleration of about 10000 G for 1 to 60 minutes) again in water having almost the same volume as that of the cream component.
• the stability and heat-sensitive coagulation properties of the latex can be sufficiently maintained by the water-soluble polymer which is previously added before the deproteinization treatment and remained even after the purification treatment.
• the degree of the deproteinization attained in the present invention is adjusted so that the nitrogen content (N%) as determined by the Kjeldahl method is 0.1% or less, preferably 0.05% or less, and more preferably 0.02% or less.
• the degree of the deproteinization can also be confirmed by the presence or absence of adsorption and degree of adsorption on the basis of the protein by means of an infrared absorption spectrum.
• an absorption at 3320 cm ⁇ 1 derived from short-chain peptide or amino acid may be observed.
• an absorption at 3280 cm 1 derived from polymer peptide as a cause for allergy is small. It is more preferable that any absorption at 3280 cm ⁇ 1 is not observed.
• the method of producing a rubber product according to the present invention is characterized in that:
• the compound latex used to produce the dipped product by the direct method is obtained by incorporating at least a vulcanizing agent into a natural rubber latex deproteinized by the method described above.
• This compound latex is used as the raw material in the production of dipped products made of a thin film, such as surgical glove and condom.
• Examples of the vulcanizing agent include sulfur and organic sulfur-containing compound.
• the amount of the vulcanizing agent is not specifically limited, but is usually set within a range from 0.5 to 3 parts by weight based on 100 parts by weight of the rubber solid content of the latex.
• vulcanization compounding agents such as vulcanization accelerators, auxiliary vulcanization accelerators and vulcanization retardants can also be incorporated, in addition to the vulcanizing agents described above.
• Examples of the vulcanization accelerator include PX (zinc N-ethyl-N-phenyldithiocarbamate), PZ (zinc dimethyldithiocarbamate), EZ (zinc diethyldithiocarbamate), BZ (zinc dibutyldithiocarbamate) and MZ (zinc salt of 2-mercaptobenzothiazole). These vulcanization accelerators can be used alone or in combination.
• the amount of the vulcanization accelerator is preferably within a range from about 0.5 to 3 parts by weight based on 100 parts by weight of the rubber solid content of the latex.
• auxiliary vulcanization accelerator examples include zinc white.
• the amount of the auxiliary vulcanization accelerator is preferably within a range from about 0.5 to 3 parts by weight based on 100 parts by weight of the rubber solid content of the latex.
• Examples of the other additive include conventionally known various additives such as antioxidants, fillers, plasticizers, softeners and reinforcers.
• non-contaminating phenols such as CPL (hindered phenol) and antage W-300 [4,4′-butylidenbis-(3-methyl-6-t-butylphenol) are preferred, but amines such as octylated diphenylamine may also be used.
• the amount of the antioxidant is preferably within a range from about 0.5 to 3 parts by weight based on 100 parts by weight of the rubber solid content of the latex.
• Examples of the filler include kaolin clay, hard clay and calcium carbonate.
• the amount of the filler is preferably 10 parts by weight or less based on 100 parts by weight of the rubber solid content of the latex.
• a dispersant may be incorporated to improve dispersion of various additives described above into the rubber latex.
• the dispersant include various surfactants, particularly anionic surfactant.
• the amount of the dispersant is preferably within a range from about 0.3 to 1.0 parts by weight based the weight of the components to be dispersed.
• the stability of the latex becomes excessive and the effect of simultaneously satisfying the stability and heat-sensitive coagulation properties of the present invention is likely to be impaired and the processability is likely to be impaired by an increase in viscosity. Accordingly, in case of incorporating a surfactant as the dispersant, an attention must be paid to the amount must.
• a mold used in the production of the thin film dipped product by the direct method i.e. the above method (1), is not specifically limited and conventionally known various molds such as ceramic mold and grass mold can be used.
• the preheating temperature of the mold and the dipping time of the mold in the latex are set according to the composition of the compound latex such as kind and amount of the vulcanization compounding agent, and the thickness required to the rubber film, and is not specifically limited.
• a rubber glove having a thickness ranging from about 0.01 to 0.1 mm is produced by the method of the present invention, a mold heated previously to a temperature within a range from 30 to 100° C., preferably from 50 to 70° C., is dipped in a latex for 3 to 60 seconds, preferably about 5 to 20 seconds.
• the conditions for vulcanizing the rubber film formed on the surface of the mold are set according to the kind and amount of the vulcanization compounding agent, and the thickness of the rubber film formed on the surface of the mold, and is not specifically limited.
• vulcanization may be usually conducted at a temperature within a range from 80 to 120° C., preferably from 90 to 110° C., for 10 to 40 minutes, preferably 20 to 30 minutes.
• drying of the rubber film is not specifically limited, and may be conducted in the same manner as in conventional procedure of drying the rubber film formed by the direct (dipping) method.
• the heat-sensitive coagulable compound latex used to produce the dipped product by the heat sensitizing method is obtained by incorporating at least a vulcanizing agent and a heat sensitizer into a natural rubber latex deproteinized by the method described above.
• This heat-sensitive coagulable compound latex is used as the raw material in the production of dipped products made of a thick film, such as work glove and catheter.
• Examples of the heat sensitizer include conventionally known various heat sensitizers such as inorganic and organic ammonium salt, and water-soluble polymer type heat sensitizer.
• a water-soluble polymer type heat sensitizer is preferably used in view of maintaining the stability of the deproteinized natural rubber latex.
• Examples of the inorganic and organic ammonium salt include ammonium nitrate, ammonium acetate, and various zinc ammonium complexes.
• water-soluble polymer type heat sensitizer examples include polyvinyl methyl ether (PVME), polyalkylene glycol, polyether polyformal, and functional polysiloxane.
• PVME polyvinyl methyl ether
• a heat sensitizer having a cloud point of not less than normal temperature and not more than 100° C. is more preferred.
• the amount of the heat sensitizer is not specifically limited, but the heat sensitizer is preferably incorporated in the amount within a range from 0.1 to 10 parts by weight based on 100 parts by weight of the rubber solid content in the deproteinized natural rubber latex to improve the film forming properties.
• the amount of the heat sensitizer is particularly preferably within a range from 0.5 to 5 parts by weight.
• Examples of the vulcanizing agent used to prepare the heat-sensitive coagulable latex include the same vulcanizing agent as those used in the preparation of “compound latex.
• the amount of the vulcanizing agent is not specifically limited similar to the above “compound latex”, but is usually set within a range from 0.5 to 3 parts by weight based on 100 parts by weight of the rubber solid content of the latex.
• vulcanization compounding agents such as vulcanization accelerators, auxiliary vulcanization accelerators and vulcanization retardants can also be incorporated into the heat-sensitive coagulable compound latex, in addition to the heat sensitizers and vulcanizing agents described above.
• vulcanization accelerator and auxiliary vulcanization accelerator may be the same as those used in preparation of the above “compound latex”.
• a mold used in the production of the thick film dipped product by the direct method i.e. the above method (2), is not specifically limited and conventionally known various molds such as ceramic mold and grass mold can be used.
• the preheating temperature of the mold and the dipping time of the mold in the latex are set according to the composition of the heat-sensitive coagulable compound latex such as kind and a mount of the heat sensitizer and vulcanization compounding agent, and the thickness required to the rubber film, and is not specifically limited.
• a rubber glove having a thickness ranging from about 1 to 3 mm is produced by the method of the present invention, a mold heated previously to a temperature within a range from 70 to 140° C., preferably from 90 to 110° C., is dipped in a latex for 1 to 60 seconds, preferably about 10 to 30 seconds.
• the conditions for vulcanizing the rubber film formed on the surface of the mold are set according to the kind and amount of the vulcanization compounding agent, and the thickness of the rubber film formed on the surface of the mold, and is not specifically limited.
• vulcanization may be usually conducted at a temperature within a range from 80 to 120° C., preferably from 90 to 110° C., for 30 to 90 minutes, preferably 50 to 70 minutes.
• drying of the rubber film is not specifically limited, and may be conducted in the same manner as in conventional procedure of drying the rubber film formed by the heat sensitizing method.
• the latex was subjected to a centrifugation treatment at 13,000 rpm for 30 minutes and the cream component separated in the upper layer was taken out and then dispersed again in water having the same volume as that of the cream component to obtain a deproteinized natural rubber latex.
• the compound latex was cooled to 25° C. and the pH was adjusted to 8.5 using 10% formalin. Then, polyvinyl methyl ether as the heat sensitizer was added in the amount of 0.5 parts by weight based on 100 parts by weight of the rubber solid content in the latex.
• a ceramic test tube (having a diameter of 5 cm) preheated to 90° C. was dipped in the resulting compound latex for heat-sensitive molding for 30 seconds and then vulcanized at 100° C. for 90 minutes to obtain a rubber film.
• deproteinizing agent a mixture of an alkaline protease and sodium alginate (Example 2) or sodium polyacrylate (Example 3), carboxymethylcellulose (Example 4) or ammonium polyacrylate (Example 5) as the water-soluble polymer in a weight ratio of 2:98 was used.
• a nonionic surfactant was incorporated into the compound latex for heat-sensitive molding in Comparative Examples 1 to 3 in the total amount of 1.28 parts by weight based on 100 parts by weight of the rubber solid content.
• a high ammonia latex of a natural rubber was diluted so that the rubber solid content of becomes 30% by weight and then subjected to a centrifugation treatment at 13,000 rpm for 30 minutes.
• the cream component separated in the upper layer was taken out and then dispersed again in water having the same volume as that of the cream component to obtain a deproteinized natural rubber latex.
• the compound latex was cooled to 25° C. and the pH was adjusted to 8.5 using 10% formalin. Then, polyvinyl methyl ether as the heat sensitizer was added in the amount of 0.5 parts by weight based on 100 parts by weight of the rubber solid content in the latex.
• a ceramic test tube (having a diameter of 5 cm) preheated to 90° C. was dipped in the resulting compound latex for heat-sensitive molding for 30 seconds and then vulcanized at 100° C. for 90 minutes to obtain a rubber film.
• ratio in the column of “deproteinizing agent” is “ratio” (% by weight) of the components listed in the column of “active component”.
• amount in the same column is an amount (parts by weight) of the deproteinizing agent based on 100 parts by weight of the rubber solid content of the latex.
• “Amount” in the column of “surfactant” is an amount (parts by weight) of the nonionic surfactant based on 100 parts by weight of the rubber solid content of the latex before the addition of the heat sensitizer. In “amount” of the column of “surfactant” in Comparative Examples 1 to 3, the amount of the surfactant contained in “deproteinizing agent” was also added.
• a high ammonia latex of a natural rubber [rubber solid content: 60.0% by weight, pH 11.2, nitrogen content (N%): 0.33%] was diluted so that the rubber solid content of becomes 30% by weight.
• the latex was subjected to a centrifugation treatment at 13,000 rpm for 30 minutes and the cream component separated in the upper layer was taken out and then dispersed again in water having the same volume as that of the cream component to obtain a deproteinized natural rubber latex.
• a ceramic test tube (having a diameter of 5 cm) preheated to 50° C. was dipped in the resulting compound latex for heat-sensitive molding for five seconds. A mold was pulled up at a rate of 800 mm/min., and then the rubber film formed on the surface of the mold was dried.
• the mold was preheated again to 50° C., dipped in the compound latex for five minutes, and then pulled up at a rate of 1500 mm/min.
• Example 7 alkaline protease and sodium alginate (weight ratio: 2:98) [nitrogen content (N%): 0.019]
• Example 8 alkaline protease and sodium polyacrylate (weight ratio: 2:98) [nitrogen content (N%): 0.017]
• Example 9 alkaline protease and carboxymethylcellulose (weight ratio: 2:98) [nitrogen content (N%): 0.020]
• the latex obtained by the redispersion was subjected to a centrifugation treatment (cleaning treatment) again at 13,000 rpm for 30 minutes.
• the cream component separated in the upper layer was taken out and dispersed again in water having the same volume as that of the cream component to obtain a deproteinized natural rubber latex.
• the nitrogen content of the resulting deproteinized natural rubber latex was measured by the Kjeldahl method. As a result, it was 0.009%.
• a high ammonia latex of a natural rubber [rubber solid content: 60.0% by weight, pH 11.2, nitrogen content (N%): 0.33%] was diluted so that the rubber solid content of becomes 30% by weight.
• the latex was subjected to a centrifugation treatment at 13,000 rpm for 30 minutes and the cream component separated in the upper layer was taken out and then dispersed again in water having the same volume as that of the cream component to obtain a deproteinized natural rubber latex.
• the nitrogen content of the resulting deproteinized natural rubber latex was measured by the Kjeldahl method. As a result, it was 0.012%.
• Comparative Example 5 alkaline protease and polyoxyethylene sorbitan oleyl ester [POE sorbitan oleyl ester, manufactured from Kao Corp. under the trade name of “RHEODOL TW-O 120”] (weight ratio: 2:98) [nitrogen content (N%):0.013]
• Comparative Example 6 alkaline protease, sodium rosinate and polyoxyethylene nonyl phenyl ether [POE nonyl phenyl ether, manufactured from Kao Corp. under the trade name of “EMULGEN 920”] (weight ratio: 2:60:38) [nitrogen content (N%): 0.014]
• the compound latex was cooled to 25° C. and the pH was adjusted to 8.5 using 10% formalin. Then, polyvinyl methyl ether as the heat sensitizer was added in the amount of 0.5 parts by weight based on 100 parts by weight of the rubber solid content in the latex.
• a ceramic test tube (having a diameter of 5 cm) preheated to 90° C. was dipped in the heat-sensitive compound latex thus obtained for 30 seconds. A mold was pulled up, and then a rubber film having a film thickness of 1.5 mm was obtained by vulcanizing at 100° C. for 90 minutes.
• Example 12 In the same manner as in Example 11, except that the amount of the heat sensitizer was changed to 0.1 parts by weight (Example 12) or 5.0 parts by weight (Example 13) based on 100 parts by weight of the rubber solid content, preparation of heat-sensitive compound latexes and production of rubber films were conducted.
• Example 14 In the same manner as in Example 11, except that the amount of the heat sensitizer was changed to 0.05 parts by weight (Example 14) or 12 parts by weight (Example 15) based on 100 parts by weight of the rubber solid content, preparation of heat-sensitive compound latexes and production of rubber films were conducted.
• a high ammonia latex of a natural rubber [rubber solid content: 60.0% by weight, pH 11.2, nitrogen content (N%): 0.33%] was diluted so that the rubber solid content of becomes 30% by weight.
• the latex was subjected to a centrifugation treatment at 13,000 rpm for 30 minutes and the cream component separated in the upper layer was taken out and then dispersed again in water having the same volume as that of the cream component to obtain a deproteinized natural rubber latex.
• Example 11 In the same manner as in Example 11, except that the above latex (obtained by subjecting to a deproteinization treatment in the presence of a protease, an anionic surfactant and a nonionic surfactant) was used as the deproteinized natural rubber latex in place of the latex obtained by subjecting to a deproteinization treatment in the presence of a protease and a water-soluble polymer (Example 11), preparation of a heat-sensitive compound latex and production of a rubber film were conducted.
• a high ammonia (HA) latex used in the preparation of the deproteinized natural rubber latex was diluted so that the rubber solid content of becomes 30% by weight.
• the thickness of the resulting rubber film was measured at three points in total and an average value thereof was taken as the thickness.

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