JP7353600B2 - Composition and method for producing the composition - Google Patents

Description

The present invention relates to a composition and a method for manufacturing the composition.

By blending cellulose nanofibers (hereinafter also referred to as "CNF") into a rubber composition as a filler, it is possible to reinforce the rubber and improve tensile properties such as modulus (tensile stress) and tensile strength. For example, JP 2013-018918 A describes a step (1) of mixing rubber latex and an aqueous dispersion of cellulose fibers and then removing at least part of the water to obtain a cellulose fiber/rubber composite; A method for producing a rubber composition is described, which includes a step (2) of mixing the composite obtained in step 1) and rubber.

Because CNF has hydrophilic functional groups (hydroxyl groups and carboxy groups) on its surface, it has a strong self-cohesive force and also has poor compatibility with rubber components, so cellulose nanofibers are simply added to a rubber emulsion. Even when mixed, dried and kneaded, CNF aggregates in the rubber and cannot be defibrated and dispersed in the rubber, failing to exhibit sufficient reinforcing properties.

Although CNF itself is transparent, cellulose fibers (for example, 2,2,6,6-tetramethylpiperidine 1-oxyl (hereinafter also referred to as "TEMPO") obtained by oxidation reaction using an N-oxyl compound as a catalyst) ) Oxidized CNF) or CNF obtained from phosphate-esterified cellulose is blended into rubber, and the composite of CNF and rubber turns brown after kneading and crosslinking reaction process, and white color is required. The problem with products is that their use is restricted.

The particle size of the emulsion is usually 100 to 300 nm. When a thin CNF aqueous dispersion with a fiber width of 3 to 10 nm is mixed with polymer latex and dried, the surface of the latex polymer particles is covered with a CNF film after drying. For example, according to International Journal of Biological Macromolecules, 59 (2013), 99-104, in the case of TEMPO-oxidized CNF with a fiber width of 3.5 nm, the strength of this coating is 290 MPa. Even if the particles are kneaded with a diluted resin, there is a problem in that the CNF has a structure in which pulverized coatings or aggregates of CNF are dispersed in the matrix polymer, and the expected nanocomposite cannot be obtained.

In order to defibrate TEMPO-oxidized CNF into rubber, in order to suppress CNF agglomeration, glycerin or diethylene glycol is replaced with water in the CNF dispersion, and CNF from which water has been removed, a high boiling point water-soluble solvent, and a dispersion stabilizer are used. Attempts have been made to obtain a CNF/rubber composite by kneading a mixture of CNFs (such as cationic surfactants) into rubber and removing the high-boiling solvent by heating or drying under reduced pressure. However, the biggest problem with this method is that it takes time to remove the high boiling point solvent or requires large-scale equipment, resulting in high costs.

JP 2015-093882 A discloses a composite material having a step of removing water from a mixed liquid containing fine cellulose fibers having an average fiber width of 2 to 1000 nm and a resin emulsion and having a solid content concentration of 1.5% by mass or less. A method of manufacturing the material is disclosed. The reason why the solid content concentration is specified to be 1.5% by mass or less is to prevent the CNF concentration of the obtained composite material (masterbatch) from becoming low after drying. As described above, increasing the solid concentration of CNF increases the thickness of the CNF coating covering the latex polymer particles, making it more difficult to defibrate the CNF.

In addition, the method using rubber latex can be applied to rubbers that are commercially available as latex, but cannot be applied to rubbers for which latex is not commercially available, such as ethylene propylene rubber and hydrogenated NBR. , there were real problems.

In order to disperse CNF in the matrix, the hydroxy groups on the CNF surface are chemically modified, or in the case of anionically modified CNF, cationic substances (e.g. alkyl amines) are ionically bonded to the matrix resin. Efforts have been made to enhance the interaction between CNF and the CNF interface. A method is disclosed for improving the compatibility between a rubber component and CNF by treating CNF with a hydrophobic treatment agent. JP 2014-125607 discloses that fine modified cellulose fibers having an average fiber diameter of 1 to 200 nm and having carboxy groups are treated with a hydrophobic modification treatment agent having hydrocarbon groups to make rubber. A method of improving the dispersibility of cellulose fibers in rubber by blending is disclosed. Since rubber is basically a hydrophobic polymer (eg, ethylene propylene rubber, natural rubber is a typical hydrophobic polymer), the hydrophobic treatment agent used is one having, for example, a long-chain alkyl group. Therefore, the hydrophobic treatment must necessarily be carried out in a solvent system rather than in an aqueous system, resulting in an increase in costs.

JP 2016-147996 A discloses that a nonionic surfactant and/or a cationic surfactant is mixed with a microfibrillated plant fiber dispersion having an average fiber diameter of 1 μm or less, and the resulting mixture and A microfibrillated plant fiber/rubber composite obtained from a blended latex prepared by further mixing with rubber latex is disclosed. As the microfibrillated fibers, CNF obtained by mechanical defibration (according to the example, fiber width of 20 nm is used) is used. Furthermore, since rubber latex is used, a water-soluble surfactant is used. Since cellulose is hydrophilic and the surfactant is also water-soluble, the obtained CNF/rubber composite has poor water resistance, which poses the problem of inhibiting adhesion to other materials, for example. Furthermore, although the surfactant increases the compatibility between CNF and rubber, the interfacial interaction force is low, so rubber compositions using this composite cannot exhibit sufficient tensile properties and cause deformation. There was also the problem that permanent deformation was large when

Japanese Patent Application Publication No. 2013-018918 Japanese Patent Application Publication No. 2015-093882 Japanese Patent Application Publication No. 2014-125607 Japanese Patent Application Publication No. 2016-147996

International Journal of Biological Macromolecules, 59 (2013), 99-104

As mentioned above, various methods have been studied to improve the fibrillation and dispersibility of CNF in rubber, but the conventional techniques described above do not sufficiently improve the fibrillation and dispersion of CNF in rubber. Therefore, it is difficult to obtain a rubber composition with excellent tensile properties. In addition, when using latex, there are restrictions on the rubber type and grade, and there is a problem that CNF reinforced rubber cannot be made with latex-free rubbers such as ethylene-α olefin copolymer rubber, hydrogenated NBR, and chlorosulfonated polyethylene. There is also. Furthermore, a solvent may have to be used in the hydrophobization treatment to improve compatibility, which poses the problem of increased costs.

The present invention was made based on the above-mentioned circumstances, and its purpose is to provide a composition in which cellulose nanofibers are defibrated and dispersed, and which can produce a crosslinked rubber having excellent tensile properties. It is an object of the present invention to provide a method for producing a composition that can be produced at low cost regardless of the type of base rubber.

The invention made to solve the above problems is a composition containing a base rubber, a maleic anhydride-modified polymer, and non-chemically modified and non-modified cellulose nanofibers.

Another invention made to solve the above problems is a method for producing a composition containing a base rubber, a maleic anhydride-modified polymer, and non-chemically modified and non-modified cellulose nanofibers, the method comprising: a step of mixing the maleic anhydride-modified polymer with the aqueous dispersion of cellulose nanofibers, a step of removing water from the mixture obtained by the mixing step, and adding the base to the mixture obtained by the removing step. The method for producing a composition includes the steps of adding rubber and kneading at a temperature of 110° C. or higher.

According to the composition of the present invention, cellulose nanofibers are highly defibrated and dispersed, and a crosslinked rubber with excellent tensile properties can be produced. The method for producing the composition of the present invention allows the composition to be produced by a simple method and at low cost, regardless of the type of base rubber.

Hereinafter, the composition of the present invention and the method for producing the composition will be explained in detail.

<Composition>
The composition includes a base rubber (hereinafter also referred to as "component A"), a maleic anhydride-modified polymer (hereinafter also referred to as "component B"), and non-chemically modified and unmodified cellulose nanofibers (hereinafter also referred to as "component B"). (also referred to as "component C"). The composition may contain other components (hereinafter also referred to as "other components") other than component A, component B, and component C within a range that does not impair the effects of the present invention.

By containing component A, component B, and component C, the composition has cellulose nanofibers that are defibrated and dispersed, making it possible to produce a crosslinked rubber that exhibits excellent tensile properties. In this specification, "the cellulose nanofibers are defibrated and dispersed" refers to a state in which the aggregation of the cellulose nanofibers in the crosslinked rubber is suppressed and almost no agglomerates are visually observed. means a state in which no aggregates are observed at all, or a state in which only minute aggregates are observed. Furthermore, in this specification, "the cellulose nanofibers are highly defibrated and dispersed" means that the aggregation of the cellulose nanofibers is suppressed in the crosslinked rubber, and no aggregates are visually observed. means. The reason why the composition has such an effect by having the above-mentioned structure can be inferred as follows, for example. By using a maleic anhydride-modified polymer as the B component and non-chemically modified and unmodified cellulose nanofibers as the C component, the hydroxy groups of the cellulose nanofibers and the maleic anhydride groups of the maleic anhydride-modified polymer react. As a result, aggregation of cellulose nanofibers is suppressed, and cellulose nanofibers are defibrated and dispersed in the composition. As a result, the cellulose nanofibers are defibrated and dispersed in the crosslinked rubber produced using the composition, and the cellulose nanofibers exhibit high reinforcing properties, thereby exhibiting excellent tensile properties.

As mentioned above, since the crosslinked rubber produced using the composition exhibits excellent tensile properties, the composition can be suitably used as an additive for rubber for the purpose of reinforcing rubber. can.

Each component contained in the composition will be explained below.

[A component]
The base rubber that is component A is not particularly limited, and includes, for example, emulsion polymerization of natural rubber (NBR), isoprene rubber (IR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene (CR), etc. Rubber manufactured by (rubber containing latex): butadiene rubber (BR), butyl rubber (IIR), ethylene propylene copolymer rubber (EPDM, EPM), ethylene-α olefin copolymer rubber, hydrogenated acrylonitrile-butadiene rubber (H-NBR), chlorosulfonated polyethylene (CSM), and epichlorohydrin rubber (CO, ECO), which are not produced by emulsion polymerization (rubber without latex). Among these, rubbers not produced by emulsion polymerization are preferred, and ethylene propylene copolymer rubber, ethylene-α olefin copolymer rubber, hydrogenated acrylonitrile-butadiene rubber, chlorosulfonated polyethylene rubber, or combinations thereof are more preferred. The composition can contain one or more types of A component.

The lower limit of the content of component A in the composition is preferably 10% by mass, more preferably 20% by mass, based on all the components contained in the composition. The upper limit of the content ratio is preferably 50% by mass, more preferably 40% by mass, based on all the components contained in the composition. If the content ratio is less than the lower limit, the composition may become too hard to be kneaded into rubber. If the content ratio exceeds the upper limit, the melt viscosity of the composition will be too low, causing shearing during kneading. It becomes difficult for force to act, which may cause poor fibrillation of cellulose nanofibers.

In addition, as component A, when the composition is used as a masterbatch for producing crosslinked rubber, it is preferable to use the same type of rubber as the type of rubber to which the composition is added. In this case, the component A may be completely the same as the rubber type to which the composition is added, or it may be the same type but of a different grade. Examples of different grades include, for example, when ethylene propylene copolymer rubber is used as component A, those with different Mooney viscosities and those with different ethylene contents.

[B component]
The maleic anhydride-modified polymer that is component B is a polymer obtained by modifying a base polymer with maleic anhydride. Maleic anhydride groups introduced by modifying the base polymer with maleic anhydride react with hydroxyl groups on the surface of cellulose nanofibers to strengthen the interaction between cellulose nanofibers and the polymer. By chemically bonding with the surface of cellulose nanofibers, cellulose nanofibers can be dispersed in the base rubber.

The base polymer is not particularly limited, and examples include polyethylene, polypropylene, ethylene-polypropylene copolymer, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylate Examples include acid ester copolymers, acrylonitrile-butadiene rubber, and styrene-butadiene rubber.

The method of modifying the base polymer with maleic anhydride is not particularly limited, and can be carried out according to a conventional method. For example, there is a method in which maleic anhydride is graft-polymerized onto a base polymer by mixing the base polymer and maleic anhydride and heating in the presence of a small amount of peroxide, or a method in which a small amount of maleic anhydride is added during polymerization of the base polymer. Examples include a method of copolymerizing them by coexisting with each other.

Component B is preferably a latex-derived polymer (hereinafter also referred to as "maleic anhydride-modified polymer latex"). When component B is a polymer derived from latex, component B and component C can be homogeneously mixed. As a result, aggregation of CNFs can be suppressed, and CNFs can be highly defibrated and dispersed in the composition. In this specification, "derived from latex" means that a maleic anhydride-modified polymer in a latex state is used as a component that provides the maleic anhydride-modified polymer in the composition when preparing the composition.

The method for obtaining the maleic anhydride-modified polymer in a latex state is not particularly limited, and can be carried out according to a conventional method. For example, there is a method in which a maleic anhydride-modified polymer is dissolved in a soluble solvent, emulsified by high-speed stirring with water in the presence of an emulsifier if necessary, and then the solvent is removed, or the monomers constituting the base polymer are anhydrous. Examples include a method of emulsion polymerization in the presence of maleic acid.

When component B is a latex-derived polymer, component B is present in the form of particles. The lower limit of the average particle diameter of these particles is preferably 50 nm. If the average particle diameter is less than the lower limit, it will be difficult to prepare the latex, and there is a possibility that it will be necessary to add a large amount of emulsion stabilizer such as a surfactant to ensure emulsion stability. The upper limit of the average particle diameter is preferably 300 nm. If the above average particle diameter exceeds the above upper limit, the surface area of the latex polymer particles will become smaller and CNF will exist in multiple layers on the surface of the particles, which may cause CNF to aggregate between the layers and make defibration difficult. There is. In this specification, the average particle diameter of component B is the Z average particle diameter measured with a dynamic light scattering particle diameter measuring device ("Malvern Nano-ZS" manufactured by Malvern Panalytical).

The melting point or softening temperature of component B is preferably less than 110°C, more preferably less than 90°C. If the melting point or softening temperature of component B exceeds the above range, it is necessary to increase the kneading temperature when kneading the obtained CNF/maleic anhydride-modified polymer mixture and rubber, giving excessive thermal history to the CNF. , there is a risk of causing decomposition and discoloration of CNF. In this specification, the melting point of component B is a value measured by DSC method, and the softening temperature of component B is a value measured by Vicat softening point measuring method (ISO306).

The upper limit of the content of maleic anhydride groups in component B is preferably 0.7 mmol/g, more preferably 0.4 mmol/g. If the content of maleic anhydride groups exceeds the above upper limit, the polarity of component B may become too high and the compatibility with the base rubber may decrease. The lower limit of the content ratio is preferably 0.05 mmol/g, more preferably 0.1 mmol/g. If the content of maleic anhydride groups is less than the above-mentioned lower limit, it will be necessary to increase the blending amount of component B, which may impair the properties of the base rubber.

In addition, the compatibility with the base rubber changes depending on the type of base polymer of the maleic anhydride-modified polymer and the content ratio (acid value) of maleic anhydride groups in the maleic anhydride-modified polymer, so component B is different from component A. It is preferable to select in consideration of the compatibility of. For example, when an ethylene propylene copolymer rubber or an ethylene-α olefin copolymer rubber is used as the A component, it is preferable to use a maleic anhydride-modified polyolefin as the B component. Furthermore, maleic anhydride-modified polyolefins are preferred because they do not cause compatibility problems even when hydrogenated acrylonitrile-butadiene rubber is used as the A component.

[C component]
The cellulose nanofibers (component C) of the present invention are non-chemically modified and non-modified cellulose nanofibers. Examples of chemically modified cellulose nanofibers include cellulose nanofibers obtained by oxidation reaction using an N-oxyl compound such as 2,2,6,6-tetramethylpiperidine 1-oxyl as a catalyst (TEMPO oxidized cellulose nanofibers). Although there are anion-modified cellulose nanofibers obtained by phosphoric acid esterification of cellulose nanofibers and the like, the C component has not been subjected to such chemical modification or modification.

For example, in TEMPO-oxidized cellulose nanofibers, the primary hydroxyl group of the glucose ring in cellulose is selectively oxidized to become a carboxy group, which exists in the form of a sodium salt, etc., and remains on the surface of the cellulose nanofiber. The hydroxy group is only a secondary hydroxy group. In this case, it is thought that the reaction between the secondary hydroxyl group and the maleic anhydride group in component B is unlikely to occur due to the influence of steric hindrance of the sodium salt of the carboxy group. Therefore, in this composition, by using non-chemically modified and unmodified cellulose nanofibers as the cellulose nanofibers, the primary hydroxyl groups are not chemically modified, so that the hydroxyl groups and the maleic anhydride groups can be combined. Reactions are more likely to occur.

The C component is preferably one that has been mechanically defibrated. In addition to the above-mentioned mechanical defibration, chemical defibration is a method for defibrating cellulose nanofibers. Chemically defibrated cellulose nanofibers usually have a thin fiber diameter of about 3 to 4 nm, so in order to ensure fluidity of the dispersion when mixed with polymer latex, for example, the concentration of cellulose nanofibers should be reduced to 1%. It is necessary to set it to a certain degree. In this case, it is necessary to finally remove 99% of the water, which causes problems in terms of ensuring productivity and consuming a large amount of energy during processing. Further, chemically defibrated cellulose nanofibers have the disadvantage that they are more likely to discolor when heated than mechanically defibrated cellulose nanofibers. In the case of mechanically defibrated cellulose nanofibers, there are no disadvantages associated with chemically defibrated cellulose nanofibers as described above.

The fiber diameter of the C component can be appropriately selected depending on the mass ratio of the B component and the C component, the particle diameter in the case of using maleic anhydride-modified polymer latex as the B component, and the like. The lower limit of the fiber diameter is preferably 10 nm, more preferably 20 nm. If the above fiber diameter is less than the above lower limit, the thickness of the CNF layer when CNF covers the particles of maleic anhydride modified polymer latex is formed by multiple CNF layers, and Defibration during kneading may become difficult. The upper limit of the fiber diameter is preferably 300 nm, more preferably 100 nm. When the fiber diameter exceeds the above upper limit, the anisotropy of the physical properties of the crosslinked rubber produced using the composition may pose a problem.

The lower limit of the content of the C component in the composition is preferably 15% by mass, more preferably 20% by mass, based on all the components contained in the composition. If the content ratio is less than the lower limit, the viscosity of the composition will be low and the shear force will be low, which may result in insufficient fibrillation of the cellulose nanofibers. The upper limit of the content ratio is preferably 33% by mass, more preferably 30% by mass. If the content ratio exceeds the upper limit, it may be difficult to achieve uniformity when kneading with the base rubber. On the other hand, when the content of component C is within the above range, a crosslinked rubber composition in which cellulose nanofibers are highly defibrated and dispersed can be produced. In addition, the content ratio of the said C component means the content ratio of a solid content state. As used herein, "solid state" means a state excluding the solvent (water).

The lower limit of the solid mass ratio (C component/B component) of component C and component B is preferably 1/4, more preferably 1/3. When the mass ratio is less than the lower limit, the content of cellulose nanofibers is too low, and when attempting to obtain a composite containing a large amount of cellulose nanofibers, the amount of maleic anhydride-modified polymer relative to the base rubber becomes too large. There is a risk of degrading the properties of the base rubber. The upper limit of the mass ratio is preferably 1/1, more preferably 1/1.5. If the content ratio exceeds the upper limit, it may be difficult to achieve uniformity when kneading with the base rubber.

[Other ingredients]
The composition may contain other components other than component A, component B, and component C within a range that does not impair the effects of the present invention. Other components include, for example, various additives used when producing crosslinked rubber. Examples of such additives include reinforcing fillers such as carbon black, silica, and clay, stearic acid, plasticizers, process oil, and the like. The content ratio of other components in the composition can be appropriately set depending on the types of components used within a range that does not impair the effects of the present invention.

[Uses of the composition]
As mentioned above, the composition has cellulose nanofibers dispersed and defibrated, and can produce crosslinked rubber that exhibits excellent tensile properties, so it can be suitably used as an additive for rubber. . In particular, the composition can be suitably used as a masterbatch for producing crosslinked rubber.

Crosslinked rubber produced using the composition exhibits excellent tensile properties. Furthermore, energy loss during deformation is reduced. Furthermore, discoloration is suppressed. It also has a low density.

Therefore, such crosslinked rubber is very useful as a material for, for example, power transmission belts, conveyor belts, automobile tires, shoes, etc., which are subject to repeated strain. In particular, for footwear such as shoes, it is required to be white, light, and have high impact resilience, so the crosslinked rubber manufactured using this composition is an excellent product that can meet these requirements. It is.

Crosslinked rubber can be produced by adding to the composition, which is a masterbatch, the components necessary for the final product. The above components include, for example, base rubber, reinforcing fillers such as carbon black, silica, and clay, pigments, anti-aging agents, antiozonants, stearic acid, zinc oxide, plasticizers, process oils, tackifiers, and crosslinking agents. Examples include agents. Moreover, a foaming agent is also mentioned as a component other than the above.

Examples of the crosslinking agent include sulfur vulcanization type crosslinking agents (sulfur, vulcanization accelerator, zinc oxide and stearic acid), peroxide vulcanization type crosslinking agents (organic peroxide and co-crosslinking agent), etc. . Among these, peroxide vulcanization-based crosslinking agents are preferred because they have the possibility of covalently bonding the maleic anhydride-modified polymer and the base rubber. Moreover, crosslinking can also be performed by radiation crosslinking.

Examples of organic peroxides include dicumyl peroxide, t-butylperoxybenzene, di-t-butylperoxy-diisopropylbenzene, etc., and examples of sulfur-based vulcanizing agents include sulfur, morpholine disulfide, etc. . Co-crosslinking agents include polyfunctional monomers such as ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, triallylisocyanurate, polyvalent metal salts of methacrylic acid or acrylic acid, N,N'-m-phenylene bismaleimide, etc. bismaleimide etc. can be used.

In the case of a sulfur-based vulcanization system, the sulfur content (total amount of sulfur and sulfur content of the sulfur donor) is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of rubber. It is preferable to mix parts by mass. Examples of vulcanization accelerators that can be used include thiazoles such as 2-mercaptobenzothiazole (MTB), di-2-dibenzothiazyl disulfide (MBTS), and N-cyclohexyl-2-benzothiazyl sulfenamide (CBS). system; N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N-tert-butyl-2-benzothiazylsulfenamide (TBBS), N-oxydiethylene-2-benzothiazolesulfenamide, etc. Sulfenamide type; Examples include guanidine type vulcanization accelerators such as diphenylguanidine (DPG). The amount used is preferably 0.1 to 5.0 parts by mass, more preferably 0.2 to 3.0 parts by mass, per 100 parts by mass of rubber.

<Method for manufacturing composition>
The method for producing the composition is the method for producing the composition described above, which includes a step of mixing a maleic anhydride-modified polymer in a latex state and an aqueous dispersion of cellulose nanofibers (hereinafter also referred to as "mixing step"). ), a step of removing water from the mixture obtained in the above mixing step (hereinafter also referred to as "removal step"), adding the above base rubber to the mixture obtained in the above removing step, and adding the base rubber to the mixture obtained in the above removing step, The method includes a step of kneading at a temperature (hereinafter also referred to as a "kneading step").

According to the method for producing the composition, the above-mentioned composition can be produced at low cost by a simple method regardless of the type of base rubber.

Each step included in the method for producing the composition will be described below.

[Mixing process]
In this step, a maleic anhydride-modified polymer in a latex state and an aqueous dispersion of cellulose nanofibers are mixed. The maleic anhydride-modified polymer used in this step is described as the B component in the above-mentioned composition, and the cellulose nanofiber is described as the C component in the above-mentioned composition.

The method of mixing the maleic anhydride-modified polymer in a latex state with the aqueous dispersion of cellulose nanofibers is not particularly limited, and can be carried out according to a conventional method. For example, a method may be used in which a maleic anhydride-modified polymer in a latex state and an aqueous dispersion of cellulose nanofibers are weighed to a predetermined solid content ratio and mixed using a mixer or the like. In addition, for defoaming and uniform mixing, it is preferable to use an autorotating/revolving mixer as the mixer.

In this step, it is preferable to obtain a uniform mixture of the maleic anhydride-modified polymer and the cellulose nanofibers in a latex state. If the CNF is not mixed uniformly in the resulting mixture, the non-uniform CNF will not be defibrated during kneading with the base rubber, and will act as foreign matter, which may reduce the tensile properties of the crosslinked rubber. The conditions for mixing the maleic anhydride-modified polymer in the latex state and the cellulose nanofibers are not particularly limited as long as they can uniformly mix the maleic anhydride-modified polymer in the latex state and the cellulose nanofibers in the resulting mixture. For example, it can be appropriately determined depending on the amount of maleic anhydride-modified polymer and cellulose nanofiber in the latex state used.

[Removal process]
In this step, water is removed from the mixture obtained in the mixing step. Through this step, water is removed from the mixture of maleic anhydride-modified polymer and cellulose nanofibers in a latex state, and a solid mixture is obtained.

The method for removing water from the above mixture is not particularly limited, and can be carried out in accordance with a conventional method. For example, the above mixture is placed in a container with a large surface area and heated in an oven, the above mixture is kneaded in an open state while heating in a batch kneader such as a kneader, the above mixture is kneaded, heated and degassed. Examples include a method of continuously charging the mixture into a multi-screw kneading device, a method of performing spray drying, and the like.

The conditions for removing water from the above mixture are not particularly limited and can be determined as appropriate. For example, when heating in an oven, the heating temperature can be 40 to 100° C. and the heating time can be about 10 to 80 hours. Note that the heating time can be determined by, for example, tracking the mass of the mixture and determining the end of heating when no decrease in mass is observed. Moreover, the moisture content in the mixture after removing water is preferably 5% or less.

[Kneading process]
In this step, the base rubber is added to the mixture obtained in the removal step and kneaded at a temperature of 110° C. or higher.

In this step, by kneading at a temperature of 110° C. or higher, the reaction between the maleic anhydride groups in the maleic anhydride-modified polymer and the hydroxyl groups in the cellulose nanofibers proceeds. The upper limit of the kneading temperature is preferably 180°C, more preferably 160°C. If the kneading temperature exceeds the above upper limit, the cellulose nanofibers may be oxidized and discolored.

The base rubber used in this step is described as component A in the above-mentioned composition.

The kneading method is not particularly limited and can be carried out in accordance with conventional methods. For example, it can be carried out using ordinary equipment for rubber kneading (two rolls, kneader, Banbury, etc.).

In addition, in this step, the components exemplified as components used in producing crosslinked rubber in the above-mentioned composition may be added.

EXAMPLES Hereinafter, the present invention will be specifically explained based on Examples, but the present invention is not limited to the following Examples.

Details of components A to C used in the following Examples and Comparative Examples are shown below.

<Component A: Base rubber>
(A-1): Ethylene propylene copolymer rubber (JSR Corporation "EP24")
<Component B: Maleic anhydride modified polymer>
(B-1): Maleic anhydride-modified polymer latex (“Hardren NZ1015” manufactured by Toyobo Co., Ltd. (particle diameter 170 nm, solid content concentration 30% by mass, melting point 80°C))
<Component C: Cellulose nanofiber>
(C-1): Cellulose nanofiber aqueous dispersion (Sugino Machine Co., Ltd.'s "Binfis WF-0-100" (non-chemically modified and unmodified, solid content concentration: 5.9% by mass, average fiber diameter: 10 ~50nm))
(C-2): TEMPO oxidized cellulose nanofiber dispersion (Nippon Paper Industries'"Selenpia 1% dispersion" (average fiber diameter: 3.5 nm))

<Preparation of composition>
[Example 1-1] Preparation of composition (S-1) 400 g of (C-1) and 157.3 g of (B-1) were weighed into a beaker, and after mixing, A mixture was obtained by stirring the mixture uniformly using a foam remover (Rentaro). This mixture was placed in a tray of 300 x 230 x 50 mm, dried in an oven at 40°C for 96 hours, and further dried under reduced pressure at 70°C to completely remove volatile components to obtain a dried product. 30 g of this dry product and 10 g of (A-1) were mixed and kneaded for 30 minutes using a 3-inch open rubber roll while keeping the roll temperature at 110 to 120°C. Obtained.

[Example 1-2] Preparation of composition (S-2) Same as Example 1 except that 196.7 g of (B-1) was used and 35 g of dried material and 26 g of (A-1) were mixed. A composition (S-2) was obtained.

[Example 1-3] Preparation of composition (S-3) In the same manner as in Example 1, except that 118 g of (B-1) was used and 25 g of the dry material and 6 g of (A-1) were mixed. A composition (S-3) was obtained.

[Example 1-4] Preparation of composition (S-4) Composition (S-4) was obtained in the same manner as in Example 2, except that (A-1) was changed to 35 g.

[Example 1-5] Preparation of composition (S-5) Composition (S-5) was obtained in the same manner as in Example 3, except that (A-1) was changed to 4 g.

[Comparative Example 1-1] Preparation of Composition (CS-1) Composition (CS-1) was prepared in the same manner as in Example 1 except that 500 g of (C-2) was used instead of (C-1). I got it.

Table 1 below shows the compositions of compositions (S-1) to (S-5) and (CS-1). In addition, in Table 1 below, the content ratio of each component is a value based on the total amount of the composition as 100% by mass. Further, in Table 1 below, the content ratios of component B and component C are the content ratios as solid content.

<Preparation of crosslinked rubber sheet>
Details of the components used in Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-5 are shown below.
Base rubber: ethylene propylene copolymer rubber (JSR Corporation "EP24")
Cross-linking agent: dicumyl peroxide (“Percumyl D” from NOF Corporation)
Carbon black: HAF (“Seest 3” by Tokai Carbon Co., Ltd.)

[Example 2-1] Preparation of crosslinked rubber sheet (G-1) 23.33 g of base rubber was wound around an open roll, 13.33 g of the composition (S-1) prepared above was added, and the open roll was wound. After kneading for 8 to 10 minutes, 0.83 g of crosslinking agent was added and kneading was carried out at a roll temperature of 60 to 70°C. Next, the gap between the rolls was closed and the mixture was passed through three times to complete the kneading. The obtained kneaded product was sheeted to a thickness of 1.1 to 1.2 mm using the open roll described above. Next, the mixture was heated and pressed at a hot plate temperature of 165° C. for 25 minutes to effect crosslinking, thereby obtaining a crosslinked rubber sheet (G-1) with a thickness of 1.0 mm.

[Examples 2-2 to 2-6] Production of crosslinked rubber sheets (G-2) to (G-6) Example 2- Crosslinked rubber sheets (G-2) to (G-6) having a thickness of 1.0 mm were obtained in the same manner as in Example 1.

[Comparative Example 2-1] Production of cross-linked rubber sheet (CG-1) A cross-linked rubber sheet (CG-1) with a thickness of 1.0 mm was prepared in the same manner as in Example 2-1, except that the types and amounts of each component shown in Table 2 below were used. A crosslinked rubber sheet (CG-1) was obtained.

[Comparative Example 2-2] Production of cross-linked rubber sheet (CG-2) 33.33 g of base rubber and 0.83 g of cross-linking agent were mixed, kneaded at a roll temperature of 60 to 70°C, and passed through three times. . Next, it was sheeted to a thickness of 1.1 to 1.2 mm, and heated and pressed at a hot plate temperature of 165° C. for 25 minutes to effect crosslinking, thereby obtaining a crosslinked rubber sheet (CG-2) with a thickness of 1.0 mm.

[Comparative Example 2-3] Production of crosslinked rubber sheet (CG-3) (B-1) was dried to obtain a dry polymer. 6.67 g of this dry polymer and 26.67 g of base rubber were kneaded for 10 minutes using a 3-inch open roll for rubber, keeping the roll temperature at 110 to 120°C. Once taken out from the roll and cooled, the roll temperature was maintained at 70 to 80°C, 0.83 g of crosslinking agent was added, kneaded, and passed through three times. Next, it was sheeted to a thickness of 1.1 to 1.2 mm, and heated and pressed at a hot plate temperature of 165° C. for 25 minutes to effect crosslinking, thereby obtaining a crosslinked rubber sheet (CG-3) with a thickness of 1.0 mm.

[Comparative Example 2-4] Production of crosslinked rubber sheet (CG-4) 33.33 g of base rubber was wound around a roll, and kneaded for a total of 10 minutes while 6.67 g of carbon black was added in portions. Next, 0.83 g of crosslinking agent was added and kneaded. Next, the gap between the rolls was closed and the mixture was passed through three times to complete the kneading. It was sheeted to a thickness of 1.1 to 1.2 mm, and heated and pressed at a hot plate temperature of 165° C. for 25 minutes to effect crosslinking, thereby obtaining a crosslinked rubber sheet (CG-4) with a thickness of 1.0 mm.

[Comparative Example 2-5] Production of cross-linked rubber sheet (CG-5) A cross-linked rubber sheet (CG-5) with a thickness of 1.0 mm was prepared in the same manner as in Comparative Example 2-4, except that carbon black was changed to 13.33 g. ) was obtained.

Table 2 below shows the compositions of the crosslinked rubber sheets (G-1) to (G-6) and (CG-1) to (CG-5). In Table 2 below, the unit of content of each component is "g".

<Evaluation>
The crosslinked rubber sheet produced above was evaluated for dispersibility and tensile properties using the following methods. Further, the crosslinked rubber sheets obtained in Examples 2-1 to 2-4 and Comparative Example 2-1 were evaluated for discoloration by the following method. The results are also shown in Table 2 below. Note that in Table 2 below, "-" indicates that the corresponding evaluation was not performed. Furthermore, the dynamic viscoelastic properties of the crosslinked rubber sheets obtained in Example 2-1 and Comparative Example 2-5 were measured by the following method. The results are shown in Table 3 below.

[Dispersibility evaluation]
Each of the obtained crosslinked rubber sheets was visually observed to determine whether aggregates were observed. Dispersibility was evaluated as "A" (extremely good) if no aggregates were observed by visual observation, and "B" (good) if minute aggregates were observed. Those in which this was observed were evaluated as "C" (poor).

[Tensile property evaluation]
Each of the obtained crosslinked rubber sheets was punched out using a No. 6 dumbbell and subjected to a tensile test using a tensile tester ("SHIMADZU AUTOGRAPH AGS-X 5kN" manufactured by Shimadzu Corporation) at a tensile speed of 500 mm/min to determine the tensile strength. (Tb), tensile elongation (Eb) and tensile stress (M50 and M100) were measured. The tensile properties were evaluated using the tensile strength (Tb), elongation at break (Eb), and tensile stress (M50 and M100) of the crosslinked rubber sheet (CG-2) as standards for each tensile property. This was done by comparing the values of the characteristics.

[Discoloration evaluation]
The color tone of each of the obtained crosslinked rubber sheets was visually observed. The evaluation of discoloration is determined by visually observing whether the color is brown or not. Those with no discoloration are rated "A" (good), and those with discoloration are graded "B" ( Poor).

[Measurement of density]
The density (unit: mg/m ³ ) of each obtained crosslinked rubber sheet was measured according to JIS K 6268 (1998).

[Measurement of dynamic viscoelastic properties]
The dynamic viscoelastic properties (E' and tan δ) were measured using "DMA7100" manufactured by Hitachi High-Tech Science Co., Ltd. The sample size was 1 mm thick, 4 mm wide, and the distance between chucks was 20 mm, the frequency was 1 Hz, the target amplitude was 10 μm, The measurement was performed automatically with a minimum tension of 50 mN, a tension gain of 1.5, and an initial tension amplitude of 200 mN.

As is clear from the results in Table 2, the crosslinked rubber sheet manufactured using the composition of the example had a lower Cellulose nanofibers were dispersed and defibrated, and exhibited excellent tensile properties.

Furthermore, the crosslinked rubber sheet produced using the composition of the example had suppressed discoloration compared to the crosslinked rubber sheet (CG-1) produced using the composition of the comparative example.

Furthermore, the crosslinked rubber sheets produced using the compositions of Examples had lower densities than the crosslinked rubber sheets containing carbon black (CG-4 and CG-5).

The crosslinked rubber sheet manufactured using the composition of Example 2-1 has a low tan δ despite having a high elastic modulus compared to the crosslinked rubber sheet containing carbon black (CG-5). Indicated. This shows that by using the composition of the present invention, a crosslinked rubber with low hysteresis loss can be produced.

Claims (8)

base rubber,
maleic anhydride-modified polymer,
Contains non-chemically modified and non-modified cellulose nanofibers,
A composition wherein the maleic anhydride-modified polymer is a latex-derived polymer . The composition according to claim 1, wherein the base rubber is ethylene propylene copolymer rubber, ethylene-α olefin copolymer rubber, hydrogenated acrylonitrile-butadiene rubber, chlorosulfonated polyethylene rubber, or a combination thereof. The composition according to claim 1 or 2, wherein the maleic anhydride-modified polymer has a melting point or softening temperature of less than 110°C. The composition according to any one of claims 1 to 3 , wherein the maleic anhydride-modified polymer is a maleic anhydride-modified polyolefin. The composition according to any one of claims 1 to 4 , wherein the cellulose nanofibers are mechanically defibrated. The composition according to any one of claims 1 to 5 , wherein the content of the cellulose nanofibers is 15% by mass or more and 33% by mass or less. The composition according to any one of claims 1 to 6 , which is used as an additive for rubber. base rubber,
maleic anhydride-modified polymer,
A method for producing a composition containing non-chemically modified and non-modified cellulose nanofibers,
mixing the maleic anhydride-modified polymer in a latex state and the aqueous dispersion of cellulose nanofibers;
a step of removing water from the mixture obtained by the mixing step;
A method for producing a composition comprising: adding the base rubber to the mixture obtained in the removing step and kneading at a temperature of 110° C. or higher.