JP2019085497A - Natural rubber composition and adhesive - Google Patents

Abstract

To provide a natural rubber composition that, compared with the case where natural rubber is used alone, sufficiently suppresses deterioration of breaking elongation while securing sufficiently high tension stress (moduli) and breaking strength, and has properties such as tension stress, breaking strength and breaking elongation at sufficiently high levels in a balanced manner.SOLUTION: A natural rubber composition contains a natural rubber and a water-soluble polysaccharide that is contained in an amount of 0.01-9 pts.mass relative to 100 pts.mass of the natural rubber.SELECTED DRAWING: None

Description

  The present invention relates to natural rubber compositions and adhesives.

  Natural rubber is a natural and environmentally friendly material, and also has excellent performance that can not be exhibited by synthetic rubber. Various rubber compositions containing natural rubber have been studied to take advantage of such properties of natural rubber. For example, in JP 2009-191198 A (Patent Document 1), a rubber composition containing cellulose nanofibers (cellulose nanofibers) and a silane coupling agent in a rubber component is disclosed, and in the example, the rubber component An example using natural rubber latex is disclosed. Further, JP-A-61-73748 (Patent Document 2) discloses a rubber composition in which 20 to 40 parts by mass of a water-soluble polymer substance is mixed with 100 parts by mass of a natural rubber latex.

JP, 2009-191198, A Japanese Patent Application Laid-Open No. 61-73748

  However, the natural rubber composition containing natural rubber and cellulose nanofibers is significantly reduced in elongation at break as compared with the case where natural rubber is used alone, and it is not always sufficient from the viewpoint of elongation at break. It was not. Further, in the conventional rubber composition as described in Patent Document 2 as well, the elongation at break is also reduced as compared with the case where natural rubber is used alone, and the reduction in elongation at break is sufficiently suppressed. I could not

  The present invention has been made in view of the problems of the prior art, and has sufficiently high tensile stress (modulus) and breaking strength as compared with the case of using natural rubber alone. A natural rubber composition capable of sufficiently suppressing the reduction of breaking elongation while being able to have properties such as tensile stress, breaking strength and breaking elongation at a sufficiently high level in a well-balanced manner, and An object of the present invention is to provide an adhesive comprising the natural rubber composition.

  As a result of intensive studies to achieve the above object, the present inventors contain natural rubber and a water-soluble polysaccharide whose content is 0.01 to 9 parts by mass with respect to 100 parts by mass of the natural rubber. The natural rubber composition makes it possible to sufficiently increase the tensile stress (modulus) and the breaking strength as well as sufficiently suppressing the reduction of the breaking elongation as compared with the case where the natural rubber is used alone. As a result, it has been found that it becomes possible to make natural rubber compositions have properties such as tensile stress, breaking strength and breaking elongation at a sufficiently high level in a well-balanced manner, leading to the completion of the present invention. The

  That is, the natural rubber composition of the present invention is characterized by containing a natural rubber and a water-soluble polysaccharide having a content of 0.01 to 9 parts by mass with respect to 100 parts by mass of the natural rubber. .

  In the natural rubber composition of the present invention, the water-soluble polysaccharide is preferably at least one selected from the group consisting of starch and agar.

  In the natural rubber composition of the present invention, the content ratio of the water-soluble polysaccharide to 100 parts by mass of the natural rubber is preferably 0.1 to 9 parts by mass.

  The adhesive of the present invention is characterized by comprising the above-mentioned natural rubber composition of the present invention.

  According to the present invention, it is possible to sufficiently reduce the tensile strength (modulus) and the breaking strength while sufficiently suppressing the reduction of the breaking elongation as compared with the case where the natural rubber is used alone. To provide a natural rubber composition capable of having properties such as tensile stress, breaking strength and breaking elongation at a sufficiently high level in a well-balanced manner, and an adhesive comprising the natural rubber composition. It becomes possible.

  Hereinafter, the present invention will be described in detail in line with its preferred embodiments.

[Natural rubber composition]
The natural rubber composition of the present invention is characterized by containing a natural rubber and a water-soluble polysaccharide whose content is 0.01 to 9 parts by mass with respect to 100 parts by mass of the natural rubber.

  Such a natural rubber is not particularly limited, and known natural rubbers can be appropriately used. Such a natural rubber may be, for example, one derived from natural rubber latex (rubber component in natural rubber latex). Such a natural rubber latex is not particularly limited. For example, a field latex, a high ammonia latex (high ammonia natural rubber latex), a centrifugally separated concentrated latex, a deproteinized natural rubber latex treated with a surfactant, an enzyme or the like Latex etc. can be used suitably. Such natural rubber latex may be used singly or in combination of two or more. Moreover, you may utilize a commercial item suitably as such a natural rubber latex.

  Also, such natural rubber may be, for example, technically graded rubber (TSR: Technically Specified Rubber) such as SMR (Standard Malaysian Rubber), SIR (Standard Indonesian Rubber), STR (Standard Thai Rubber), etc .; RSS); High-Purity Natural Rubber; Epoxidized natural rubber, hydroxylated natural rubber, hydrogenated natural rubber, modified natural rubber such as grafted natural rubber, etc. may be used.

  As such natural rubber, TSR and RSS are preferable from the viewpoint of being able to interact with proteins, phospholipids and the like. Moreover, as such a natural rubber, it is preferable to use natural rubber latex-derived rubber (rubber component in natural rubber latex) from the viewpoint that preparation of the natural rubber composition is easier.

  Moreover, the natural rubber composition of the present invention contains a water-soluble polysaccharide together with the above-mentioned natural rubber. As described above, since the natural rubber composition of the present invention is formed using biodegradable components such as the above natural rubber and water-soluble polysaccharides, it is suitably used also from the viewpoint of environmental load. It is possible material.

  With regard to such water-soluble polysaccharides, “water-soluble” means that the attraction between solute molecules and water molecules overcomes the attraction between solute molecules (the attraction between solute molecules and water molecules is solute molecules Higher than the attractive force), which means that the solute molecule is in a hydrated state. As such water-soluble polysaccharides, for example, starch, agar, glycogen, dextrin, glucan (β1,3-glucan), fructan (inulin-leban β2 → 6), chitin (water solubilization), carrageenan, heparin, hyaluronic acid Acid, pectin, xyloglucan and the like can be mentioned.

  As such water-soluble polysaccharides, the effect of improving physical properties is high, and from the viewpoint of cost, starch, agar, glycogen, dextrin, glucan, carrageenan, heparin, hyaluronic acid, pectin are more preferable, starch, agar are More preferred, agar is particularly preferred.

  In the natural rubber composition of the present invention, the content ratio of the water-soluble polysaccharide to 100 parts by mass of the natural rubber is 0.01 to 9 parts by mass. If the content ratio of such a water-soluble polysaccharide is less than the above-mentioned lower limit, the effect obtained by containing the water-soluble polysaccharide becomes insufficient, and on the other hand, if the above-mentioned upper limit is exceeded, the breaking elongation is made a sufficient level. And the breaking strength decreases. In addition, since the tensile stress (modulus) becomes higher, the content ratio of the water-soluble polysaccharide is 0.1 to 9 parts by mass (more preferably 0.1 to 8) with respect to 100 parts by mass of the natural rubber. It is more preferable that it is a mass part). Thus, the lower limit value of the content ratio of the water-soluble polysaccharide is preferably 0.1 part by mass from the viewpoint that the tensile stress (modulus) is higher.

  Further, the natural rubber composition of the present invention is not particularly limited, and may be made of a mixture of a natural rubber latex and a water-soluble polysaccharide. In this case, the natural rubber composition of the present invention is a composition comprising natural rubber, water and a water-soluble polysaccharide. In addition, the natural rubber composition of the present invention can be more easily made into a composition in which the water-soluble polysaccharide is sufficiently uniformly dispersed, and when a sheet or the like is produced, sufficiently high tensile stress ( Distilling water from a mixed material (mixed liquid) containing a natural rubber latex and a water-soluble polysaccharide, since it is easier to have a modulus and a breaking strength and to have a sufficiently high elongation at break. It is preferable that it is what is obtained (dried material of the said mixing raw material). Moreover, it is preferable that it is a liquid mixture of natural rubber latex and the aqueous solution of a water-soluble polysaccharide as such a mixing raw material. In a natural rubber composition formed by distilling off water from such a mixed material, natural rubber latex becomes a dried product by evaporation (drying) of water, and the dried product of natural rubber latex is contained in the composition. Will be contained. Thus, the dried product of the mixture of a natural rubber latex and a water-soluble polysaccharide obtained by distilling off water is a natural rubber latex-derived natural rubber obtained by drying a natural rubber latex, and a water-soluble polysaccharide. And a composition containing

  Here, when the water is distilled away (dried) as it is without mixing the water-soluble polysaccharide with the natural rubber latex (when the water is distilled away from the natural rubber latex as it is), the obtained natural rubber (dried) ) Are not necessarily sufficient in terms of breaking strength and modulus. This is because, when water is distilled away from the natural rubber latex as it is, in the resulting dried product, compatibility between the protein (ω end) and the phospholipid (α end) present in the outer layer of the rubber ball is difficult. The present inventors speculate that the crack is likely to occur and the mechanical strength does not increase. On the other hand, in the natural rubber composition of the present invention, by including the water-soluble polysaccharide at a predetermined concentration together with the natural rubber, the reason is not necessarily clear, but the protein (ω end) of the rubber molecule and phosphorus Since the lipid (α-terminal) and the water-soluble polysaccharide are hydrogen-bonded at an appropriate ratio and the water-soluble polysaccharide plays a role like a paste, the breaking strength of the natural rubber composition is improved in an appropriate range In addition to being able to be reduced, it is also possible to sufficiently suppress the deterioration of the elongation properties of the natural rubber composition, and furthermore, it is not possible to make the tensile stress sufficiently high. The present inventors infer. Furthermore, in the natural rubber composition of the present invention, since the polysaccharide is "water-soluble", the rubber molecule and the water-soluble polysaccharide are highly entangled in water, so, for example, natural rubber latex Even when used and dried to produce a natural rubber composition, it is possible to make physical properties such as breaking strength and modulus more advanced than when using natural rubber alone. The inventors speculate.

  The natural rubber composition of the present invention may also contain additives other than the natural rubber and the water-soluble polysaccharide. Such additives are not particularly limited, and known additives used for natural rubber compositions can be appropriately used. For example, tackifiers, plasticizers, wetting agents, fillers (carbon black, silica, carbonate Calcium, clay (may be organic clay), talc), antioxidant, light stabilizer, UV absorber, flame retardant, lubricant, pigment, dye, antibacterial agent, stabilizer, anti-aging agent, thickener Agents, preservatives, antifoaming agents, vulcanizing agents, viscosity modifiers, thixotropic agents and the like can be used. When a filler (carbon black, silica, calcium carbonate, clay (organic) clay, talc) is used as such an additive component, the content of the filler is 0.1 to 0.1 parts by mass of the natural rubber. More preferably, it is in the range of 200 parts by mass (more preferably 1 to 150 parts by mass). When other components other than the filler are used as such additional components, the content of such other components is 0.01 to 20 parts by mass with respect to 100 parts by mass of the natural rubber for each of the components. More preferably, it is in the range of part (more preferably 0.1 to 15 parts by mass).

  Also, such a natural rubber composition may further contain a synthetic rubber and / or a thermoplastic elastomer, depending on its use. That is, such a natural rubber composition comprises a natural rubber; a water-soluble polysaccharide whose content is 0.01 to 9 parts by mass with respect to 100 parts by mass of the natural rubber; a synthetic rubber and a thermoplastic elastomer The composition may be used as a rubber composition containing at least one selected component (hereinafter sometimes referred to as “other rubber component other than natural rubber”). Such synthetic rubbers are not particularly limited, and known ones can be appropriately used. For example, butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), ethylene-propylene rubber (EPM or EPDM) , Chloroprene rubber (CR), butyl rubber (IIR), acrylic rubber (ACM), chlorinated polyethylene rubber (CSM), polysulfide rubber (TR), silicone rubber, fluororubber and the like. The thermoplastic elastomer is not particularly limited, and known ones can be appropriately used. For example, olefin elastomers, urethane elastomers, ester elastomers, styrene elastomers, amide elastomers, acrylic elastomers, silicone elastomers, The elastomer etc. which are described in the patent 5918878 gazette and Unexamined-Japanese-Patent No. 2016-193970 gazette are mentioned.

  In the rubber composition of the form containing other rubber components other than such natural rubber, the content (total amount) of the other rubber components other than natural rubber is 0.1 to 0.1 parts by mass of the natural rubber. The amount is preferably 300 parts by mass (more preferably 1 to 200 parts by mass). If such content is less than the above-mentioned lower limit, even if it contains other rubber components other than natural rubber, there is a tendency that the effect derived from such other rubber components is not obtained sufficiently, and, on the other hand, If the upper limit is exceeded, the amount of natural rubber is too small, and the resulting composition tends to be less affected by the effects of the present invention.

  A method for producing such a natural rubber composition of the present invention may be any method capable of obtaining a composition containing the natural rubber and the water-soluble polysaccharide, and known natural rubber compositions The manufacturing method of can be adopted suitably. As a method for producing such a natural rubber composition of the present invention, for example, in the finally obtained natural rubber composition, the content ratio of the water-soluble polysaccharide relative to 100 parts by mass of the natural rubber is 0. Mixing the natural rubber latex and the aqueous solution of the water-soluble polysaccharide so as to be 01 to 9 parts by mass to obtain a mixed raw material (mixed liquid); and drying the mixed raw material to obtain the mixed raw material. And (iv) obtaining a natural rubber composition comprising the dried product of In addition, as a method for producing such a natural rubber composition of the present invention, it is possible to more efficiently produce a composition in which a water-soluble polysaccharide is more uniformly dispersed. It is preferred to adopt I). Hereinafter, such method (I) will be described.

  The aqueous solution of the water-soluble polysaccharide used in such method (I) may be an aqueous solution containing the above-mentioned water-soluble polysaccharide, and is not particularly limited, but 0.001 to 30 mass% of the above-mentioned water-soluble polysaccharide It is preferable that it is an aqueous solution containing preferably 0.005 to 20% by mass. If the content of such a water-soluble polysaccharide is less than the above lower limit, the concentration is too thin, and it is necessary to add a considerable amount of aqueous solution to add 0.1 to 9 parts by mass, and drying after mixing becomes difficult On the other hand, when the above upper limit is exceeded, the polysaccharide can not be uniformly dispersed in water, and the physical properties after mixing tend to be lowered.

  The amount of the aqueous solution of the natural rubber latex and the water-soluble polysaccharide used is the water-soluble polysaccharide relative to 100 parts by mass of the natural rubber in the finally obtained natural rubber composition according to the concentration of each solid content, etc. It may be appropriately designed such that the content ratio is 0.01 to 9 parts by mass.

  Moreover, in the said method (I), the method in particular with which the said natural rubber latex and the aqueous solution of the said water soluble polysaccharide are mixed is not restrict | limited, By adding the aqueous solution of the said water soluble polysaccharide in the said natural rubber latex A method of mixing may be adopted, and after the aqueous solution of the water-soluble polysaccharide is added to the natural rubber latex, the mixing may be performed by stirring. In addition, in the case of such mixing, according to the use and design of a natural rubber composition, you may add the above-mentioned additive component and other rubber components other than a natural rubber suitably.

  In the method (I), the natural rubber latex and an aqueous solution of the water-soluble polysaccharide are mixed to obtain a mixed raw material (mixed liquid), and then the mixed raw material is dried. As such a drying method, a known method capable of distilling off (evaporating and removing) and drying can be appropriately adopted, and the mixed raw material (mixed liquid) is allowed to stand for several days. A step of distilling off water and drying may be employed. Moreover, you may employ | adopt the method of making it dry in the oven of 120 degrees C or less which thermal degradation does not occur. Furthermore, when adopting these drying methods, it is preferable to decompress and make it easy to distill off water.

  Thus, in the method (I), the natural rubber composition comprising the dried material of the mixed raw material can be obtained by a simple step of drying the mixed raw material after obtaining the mixed raw material. In the method (I), since the natural rubber latex and the water-soluble polysaccharide can be mixed in the liquid state, it is also possible to obtain a composition in which the water-soluble polysaccharide is more uniformly dispersed in the natural rubber. It is possible.

  In addition, the shape in particular of the natural rubber composition obtained in this way is not restrict | limited, According to a use etc., you may shape | mold suitably. The method for such molding is not particularly limited, and a known method (for example, a pressing and the like) may be appropriately adopted.

  In addition, such a natural rubber composition may be, for example, an adhesive (may be a water-based adhesive or a hot melt adhesive), an automobile part, a tire, a hose, a belt, a sheet, a vibration-proof rubber, a roller, a lining, a rubber Pull cloth, seal material, gloves, fenders, medical rubber (syringe gaskets, tubes, catheters), gaskets (for home appliances, for construction), asphalt modifiers, boots, grips, toys, shoes, sandals, Materials for forming keypads, gears, PET bottle cap liners, etc., rubber footwear, belts, hoses, vibration proof rubber, rubber rolls, printing blankets, rubber / resin linings, rubber plates (rubber sheets), conductivity Rubber products, Sealing materials, Sheet waterproofing, Urethane coating waterproofing, Water proof sheet for civil engineering, Sealing device, Extruded rubber products, Sponge rubber products, Anti-corrosion May architectural gaskets, seismic isolation rubber, paving rubber block, non-metallic chain, medical and sanitary rubber products, rubber coated fabrics products, be suitably applied as materials for forming the rubber-plastic gloves. Such a natural rubber composition can also be applied to coating agents such as fingerprint resistant coatings for touch panels, lubricious coatings for metal surfaces, and primers for metal coating. In addition, such a natural rubber composition is more preferably used as an adhesive.

[adhesive]
The adhesive of the present invention is characterized by comprising the above-mentioned natural rubber composition of the present invention. Thus, the adhesive of the present invention comprises a natural rubber composition containing natural rubber and a water-soluble polysaccharide having a content of 0.01 to 9 parts by mass with respect to 100 parts by mass of the natural rubber. It is a feature.

  Such an adhesive is a water-based adhesive containing the natural rubber, a water-soluble polysaccharide whose content ratio is 0.01 to 9 parts by mass with respect to 100 parts by mass of the natural rubber, and water. Is preferred. Such a water-based adhesive may be made of a mixture of the natural rubber latex and the water-soluble polysaccharide. In addition, it is preferable that the quantity of such water is 1-1000 mass parts (more preferably 10-800 mass parts) with respect to 100 mass parts of said natural rubbers. If the content is less than the lower limit, it tends to be difficult to uniformly disperse in water. On the other hand, if the content exceeds the upper limit, the concentration becomes too thin and it is necessary to apply a large amount of aqueous solution. The evaporation time tends to be long and the curing time is long. Also, the method of preparing such a water-based adhesive is not particularly limited, and may be prepared, for example, by adding the water-soluble polysaccharide or the aqueous solution thereof to the natural rubber latex and mixing it. In the case, it is good also as an aqueous adhesive as it is, without distilling water out of the natural rubber composition obtained.

  Moreover, in such an adhesive, among the above-mentioned additive components, tackifiers, plasticizers, wetting agents, fillers, antioxidants, light stabilizers, ultraviolet absorbers, flame retardants, pigments, antibacterial agents, stability Agents, antiaging agents, thickeners, preservatives, antifoaming agents, vulcanizing agents, viscosity modifiers, thixotropic agents (more preferably, fillers, antioxidants, light stabilizers, ultraviolet light absorbers, flame retardants, antibacterial agents) And anti-aging agents, thickeners, preservatives, vulcanizing agents, viscosity modifiers, thixotropic agents) are preferred. In addition, in such an adhesive, when a filler (carbon black, silica, calcium carbonate, (organic) clay, talc) is used as an additive component to be contained in the composition, the content of the filler is The amount is more preferably in the range of 0.1 to 200 parts by mass (more preferably 1 to 150 parts by mass) with respect to 100 parts by mass of the rubber. When other components other than the filler are used as such additional components, the content of such other components is 0.01 to 20 parts by mass with respect to 100 parts by mass of the natural rubber for each component. It is preferable that it is (more preferably 0.1 to 15 parts by mass). If the content is less than the lower limit, the effect tends to be low because the content is less than the lower limit. On the other hand, if the content is more than the upper limit, the content tends to be poor and the mechanical strength tends to decrease.

  The method of using the adhesive of the present invention is not particularly limited, and depending on the composition (design), it may be used in the same manner as a known adhesive comprising a natural rubber composition containing natural rubber. Just do it.

  Hereinafter, the present invention will be more specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
Under the temperature condition of room temperature (25.degree. C.), starch (relative to the natural rubber latex (high ammonia latex: trade name "Halatex" manufactured by Redex Co., Ltd., concentration of 60% by mass of natural rubber (rubber content)) starch ( Kataguri flour: 80 mL of an aqueous starch solution (A) having a concentration of 0.1 g / mL (trade name "Katkuri flour" manufactured by Kobe Sangyo Co., Ltd.) is added and stirred to prepare a mixture (natural rubber composition in the form containing water) Obtained. Then, the mixed solution is poured into a 15 cm long and 12 cm wide dish so as to be about 0.5 cm high, and then allowed to stand at room temperature (25 ° C.) for 2 weeks. Water was distilled off from the mixture to obtain a natural rubber composition.

  Subsequently, 23 g of the natural rubber composition is placed in a mold having a thickness of 1.0 mm, a length of 150 mm and a width of 150 mm, and then pressing is performed under the conditions of heating temperature: 120 ° C., pressure: 18 MPa, pressing time: 5 minutes After that, the cooling press by water cooling is performed under the conditions of pressure: 18 MPa, pressurization time: 3 minutes, and taken out from the mold, a 0.9 mm thick rubber sheet (length 148 mm, made of the natural rubber composition). 148 mm wide).

(Example 2)
Example 1 was repeated except that 80 mL of starch aqueous solution (B) having a concentration of 0.1 g / mL of starch (corn starch: trade name "corn starch" manufactured by Maehara Powder Co., Ltd.) was used instead of aqueous starch solution (A). Similarly, a 0.9 mm-thick rubber sheet comprising a natural rubber composition and the natural rubber composition was obtained.

(Example 3)
In the same manner as in Example 1 except that 80 mL of an aqueous agar solution having a concentration of 0.1 g / mL of agar (trade name "Powder Agar" manufactured by IU Supernate Co., Ltd.) was used instead of the aqueous starch solution (A) There was obtained a 0.9 mm-thick rubber sheet comprising a natural rubber composition and the natural rubber composition.

(Comparative example 1)
166.7 g of natural rubber latex (High ammonia latex: trade name "Halatex" manufactured by Reditex Co., Ltd., concentration of 60% by mass of natural rubber (rubber component)) vertically to a height of about 0.5 cm After pouring into a 15 cm by 12 cm dish, water was distilled off from the natural rubber latex by standing for 2 weeks under the temperature condition of room temperature (25 ° C.) to obtain natural rubber for comparison. .

  Next, 23 g of the obtained natural rubber is placed in a mold having a thickness of 1 mm, a length of 150 mm, and a width of 150 mm, and pressing is performed under the conditions of heating temperature: 120 ° C., pressure: 18 MPa, pressing time: 5 minutes After that, the cooling press by water cooling is performed under the conditions of pressure: 18 MPa, pressurizing time: 3 minutes, and taken out from the mold, a 0.9 mm thick rubber sheet (148 mm long and 148 mm wide) made of the natural rubber is obtained. It formed.

(Comparative example 2)
A natural rubber composition for comparison and a 0.9 mm-thick rubber sheet comprising the natural rubber composition were obtained in the same manner as in Example 1 except that the amount of the aqueous starch solution (A) was changed to 160 mL. .

(Comparative example 3)
A natural rubber composition for comparison and a 0.9 mm-thick rubber sheet comprising the natural rubber composition were obtained in the same manner as in Example 2 except that the amount of the aqueous starch solution (B) was changed to 160 mL. .

(Comparative example 4)
A natural rubber composition for comparison and a 0.9 mm-thick rubber sheet comprising the natural rubber composition were obtained in the same manner as in Example 3 except that the amount of the agar aqueous solution added was changed to 160 mL.

(Comparative example 5)
A commercially available CNF dispersion in which cellulose nanofibers (CNF) are dispersed in water at a ratio of 49.6% by mass instead of the aqueous starch solution (A) (trade name “SC-L-50” manufactured by Mitsubishi Paper Industries, Ltd .: Hereinafter, a natural rubber composition for comparison and a natural rubber composition of 0.9 mm in the same manner as in Example 1 except that 16.13 g of “CNF dispersion (A)” is optionally used. A thick rubber sheet was obtained.

(Comparative example 6)
A commercially available CNF dispersion in which CNF is dispersed in water at a ratio of 2.8% by mass instead of the aqueous starch solution (A) (trade name “GC-L-03” manufactured by Mitsubishi Paper Mills, Inc .; A natural rubber composition for comparison and a 0.9 mm-thick rubber sheet comprising the natural rubber composition in the same manner as in Example 1 except that 285.71 g of CNF dispersion (B) was used. Obtained.

[Evaluation of Properties of Natural Rubber Compositions Obtained in Examples 1 to 3 and Comparative Examples 1 to 6]
<Measurement test of tensile properties>
The tensile properties were measured as follows using the rubber sheets obtained in each of the examples and the comparative examples. That is, first, a No. 3 dumbbell-shaped test piece was punched out of the rubber sheet to prepare a sample for measurement of tensile properties. Next, using the sample (No. 3 dumbbell-shaped test piece), under the conditions of a tensile speed of 500 mm / min and room temperature (25 ° C.), Toyo Seiki Co., Ltd. under the trade name “Strograph VG1E” The tensile test was conducted in accordance with JIS K6251 (issued in 2010) using 100% modulus (100% Mod [unit: MPa]), 200% modulus (200% Mod [unit: MPa]), 300% modulus ( 300% Mod (unit: MPa)), breaking strength (TB (unit: MPa)), and breaking elongation (EB (unit:%)) were measured, respectively. The obtained results are shown in Table 1. In addition, regarding the modulus shown in Table 1, when the numerical value of the modulus of a predetermined | prescribed ratio (100%, 200%, 300%) was not able to be measured by the fracture | rupture of a test piece, it describes as "immeasability". Table 1 also shows the amounts of each component used for producing the natural rubber composition, and the like.

  Each of the natural rubber compositions (Examples 1 to 3) of the present invention containing 0.01 to 9 parts by mass of water-soluble polysaccharides with respect to 100 parts by mass of natural rubber (natural rubber obtained in Comparative Example 1 It is confirmed that the 100% Mod, 200% Mod and 300% Mod are more advanced as compared with the dried product of natural rubber latex), and the breaking strength (TB) is also improved. Was confirmed. In addition, it is confirmed that all of the natural rubber compositions (Examples 1 to 3) of the present invention have a breaking elongation (EB) of 300% or more and a breaking elongation (EB) at a sufficiently high level. It was done.

  On the other hand, in a natural rubber composition (comparative examples 2 to 4) containing 16 parts by mass of water-soluble polysaccharide relative to 100 parts by mass of natural rubber, all of them are broken before giving an elongation of 300%. In contrast to the natural rubber (the dried natural rubber latex) obtained in Comparative Example 1, the breaking strength (TB) was also lowered. Furthermore, in all of the natural rubber compositions (Comparative Examples 2 to 4) containing 16 parts by mass of water-soluble polysaccharides with respect to 100 parts by mass of natural rubber, the elongation at break (EB) is less than 300% in all cases. It was also found that the decrease in EB) could not be sufficiently suppressed. In addition, in a natural rubber composition (Comparative Examples 5 to 6) using CNF, which is a non-water-soluble polysaccharide instead of a water-soluble polysaccharide (natural rubber latex obtained in Comparative Example 1 (natural rubber latex) Of the breaking strength (TB) is improved as compared to the dried product of (1), but the breaking elongation (EB) decreases significantly to 99% or less and the lowering of the breaking elongation (EB) can not be sufficiently suppressed Was confirmed.

  From these results, according to the natural rubber composition of the present invention (Examples 1 to 3) containing 0.01 to 9 parts by mass of water-soluble polysaccharide with respect to 100 parts by mass of natural rubber, tensile stress and breakage are observed. It has been found that it is possible to have properties such as strength and elongation at break at a sufficiently high level in a well-balanced manner.

  As described above, according to the present invention, the tensile strength (modulus) and the breaking strength can be made sufficiently high while the breaking elongation is reduced, as compared with the case where natural rubber is used alone. From a natural rubber composition capable of sufficiently suppressing the properties and having properties such as tensile strength, breaking strength and breaking elongation at a sufficiently high level in a well-balanced manner, and the natural rubber composition It is possible to provide an adhesive that

Thus, the natural rubber composition of the present invention is particularly useful as a material used for applications such as adhesives since it has properties such as tensile stress, breaking strength and breaking elongation at a sufficiently high level in a well-balanced manner .

Claims (4)

  What is claimed is: 1. A natural rubber composition comprising a natural rubber and a water-soluble polysaccharide whose content ratio is 0.01 to 9 parts by mass with respect to 100 parts by mass of the natural rubber.   The natural rubber composition according to claim 1, wherein the water-soluble polysaccharide is at least one selected from the group consisting of starch and agar.   The natural rubber composition according to claim 1 or 2, wherein a content ratio of the water-soluble polysaccharide to 100 parts by mass of the natural rubber is 0.1 to 9 parts by mass.   An adhesive comprising the natural rubber composition according to any one of claims 1 to 3.