Rubber additive, rubber composition, and tire

Abstract

A rubber additive according to the present invention contains an ester compound. The ester compound contains: a rosin-based ester compound having three or more ester bonds per molecule; and a fatty acid-based ester compound having three or more ester bonds per molecule.

Description

Rubber additives, rubber compositions and tires

[0001] The present invention relates to a rubber additive, a rubber composition, and a tire.

[0002] Various rubber additives have been known. More specifically, plasticizers and softeners are known as rubber additives. Plasticizers and softeners reduce the viscosity of rubber compositions. Therefore, the use of plasticizers and softeners improves the workability of kneading rubber compositions.

[0003] As a plasticizer and softener, tall oil ester oil has been proposed, for example. Tall oil ester oil is produced, for example, by esterifying tall oil (45% fatty acid, 38% rosin, acid value 157) with diethylene glycol in the presence of an ester catalyst (OH / COOH=1.2) (see, for example, Patent Document 1 (Synthesis Example 1)).

[0004] Japanese Patent Application Laid-Open No. 2008-201933

[0005] On the other hand, a molded product (rubber product) of a rubber composition may be required to have wet grip properties depending on the application. However, when a rubber composition contains the tall oil ester oil, the molded product (rubber product) of the rubber composition does not have sufficient wet grip properties.

[0006] The present invention provides a rubber additive, a rubber composition, and a tire that can provide a rubber composition having excellent low viscosity and a molded product having excellent wet grip properties.

[0007] The present invention [1] is a rubber additive containing an ester compound, and the ester compound includes a rubber additive containing a rosin-based ester compound having three or more ester bonds in one molecule and a fatty acid-based ester compound having three or more ester bonds in one molecule.

[0008] The present invention [2] includes the rubber additive according to the above [1], wherein the rosin-based ester compound contains a reaction product of a carboxy group-containing component and an alcohol component, the carboxy group-containing component contains a rosin, and the alcohol component contains a trihydric or higher alcohol.

[0009] The present invention [3] includes the rubber additive according to the above [2], in which the content of abietadienoic acid is 50 mass % or less relative to the total amount of the rosins.

[0010] The present invention [4] comprises the rubber additive according to any one of the above [1] to [3], wherein the fatty acid ester compound contains a reaction product of a carboxy group-containing component and an alcohol component, and / or contains a fat or oil, the carboxy group-containing component contains a fatty acid, and the alcohol component contains a trihydric or higher alcohol.

[0011] The present invention [5] includes the rubber additive according to the above [4], wherein the fatty acids have an iodine value of 170 or less.

[0012] The present invention [6] includes the rubber additive according to the above [1], wherein the ester compound contains a reaction product of a carboxy group-containing component and an alcohol component, the carboxy group-containing component contains a rosin and a fatty acid, and the alcohol component contains a trihydric or higher alcohol.

[0013] The present invention [7] includes the rubber additive according to the above [6], wherein the ester compound contains a product of a simultaneous reaction of the rosin, the fatty acid, and the alcohol component.

[0014] The present invention [8] includes the rubber additive according to the above [6] or [7], wherein the ester compound contains a mixture of a reaction product of the rosin and the alcohol component, and a reaction product of the fatty acid and the alcohol component.

[0015] The present invention [9] comprises the rubber additive according to any one of the above [6] to [8], wherein the fatty acids have an iodine value of 170 or less.

[0016] The present invention

[10] includes the rubber additive according to any one of the above [6] to [9], in which the content of abietadienoic acid is 50 mass% or less relative to the total amount of the rosins.

[0017] The present invention

[11] includes a rubber composition containing the rubber additive according to any one of the above [1] to

[10] .

[0018] The present invention

[12] includes a tire containing a molded product of the rubber composition described in the above

[11] .

[0019] In the rubber additive of the present invention, the ester compound contains a rosin-based ester compound having three or more ester bonds in one molecule and a fatty acid-based ester compound having three or more ester bonds in one molecule, and therefore, the rubber composition has excellent low viscosity, and further, a molded product having excellent wet grip properties can be obtained.

[0020] The rubber composition of the present invention contains the above-mentioned rubber additives and therefore has excellent low viscosity. Furthermore, this rubber composition can be used to obtain molded articles with excellent wet grip properties.

[0021] The tire of the present invention contains a molded product of the rubber composition described above, and therefore has excellent productivity and excellent wet grip properties.

[0022] 1. Rubber Additive [Ester Compound] The rubber additive contains an ester compound. Preferably, the rubber additive consists of an ester compound.

[0023] The ester compound contains a rosin-based ester compound (described below) having three or more ester bonds in one molecule and a fatty acid-based ester compound (described below) having three or more ester bonds in one molecule. The ester compound is obtained, for example, from a carboxy group-containing component and an alcohol component. Specifically, the ester compound contains a reaction product between the carboxy group-containing component and the alcohol component.

[0024] [Carboxy Group-Containing Component] The carboxy group-containing component contains rosins and fatty acids. The carboxy group-containing component preferably consists of rosins and fatty acids.

[0025] Rosins are derived from plants and contain compounds containing a carboxyl group. By using rosins, rubber additives with an excellent biomass content can be obtained. Examples of rosins include unmodified rosin and modified rosin.

[0026] An example of an unmodified rosin is natural rosin. Natural rosin is a natural resin whose main component is resin acid. Resin acid is a compound having a carboxyl group derived from trees. Resin acid is, for example, an acid having a ring structure (i.e., a non-fatty acid). Examples of the ring structure include an aromatic ring, a saturated alicyclic ring, and an unsaturated alicyclic ring.

[0027] More specifically, examples of resin acids include resin acids having conjugated double bonds and resin acids having no conjugated double bonds.

[0028] Examples of resin acids having conjugated double bonds include abietadienoic acid. Examples of abietadienoic acids include abietic acid, palustric acid, and neoabietic acid. Examples of resin acids without conjugated double bonds include dehydroabietic acid, dihydroabietic acid, and tetrahydroabietic acid. These can be used alone or in combination of two or more.

[0029] More specifically, examples of natural rosins include tall oil rosin, gum rosin, and wood rosin. These can be used alone or in combination of two or more. Tall oil rosin and gum rosin are preferred. From the viewpoint of mechanical strength, tall oil rosin is more preferred. Furthermore, from the viewpoint of low viscosity and wet grip properties, gum rosin is more preferred.

[0030] The rosin modified material is a modified material of the unmodified rosin described above. Examples of the rosin modified material include polymerized rosin, acid-modified rosin, hydrogenated rosin, phenol-modified rosin, and disproportionated rosin. These can be used alone or in combination of two or more types. Disproportionated rosin is preferred.

[0031] The rosins may be used alone or in combination of two or more kinds, and the rosins may be appropriately selected depending on the purpose and application.

[0032] More specifically, from the viewpoint of vulcanization stability, the rosin is preferably disproportionated rosin, and from the viewpoint of wet grip property, the rosin is preferably tall oil rosin or gum rosin, more preferably gum rosin.

[0033] Furthermore, as described above, rosins can contain resin acids having conjugated double bonds. Resin acids having conjugated double bonds may cause a decrease in the vulcanization stability of a rubber composition (described later). In particular, abietadienoic acids (abietic acid, palustric acid, and neoabietic acid) may cause a decrease in the vulcanization stability of a rubber composition (described later).

[0034] Therefore, from the viewpoint of vulcanization stability, the content of abietadienoic acid relative to the total amount of rosins is preferably relatively small. The content of abietadienoic acid is the total content of abietic acid, palustric acid, and neoabietic acid.

[0035] More specifically, from the viewpoint of vulcanization stability, the content of abietadienoic acid is, for example, 60% by mass or less, preferably 50% by mass or less, more preferably 35% by mass or less, even more preferably 25% by mass or less, still more preferably 15% by mass or less, and particularly preferably 5% by mass or less, relative to the total amount of rosins. The content of abietadienoic acid is, for example, 0% by mass or more, relative to the total amount of rosins. The content of abietadienoic acid is measured by GCMS analysis (mass analysis) in accordance with the examples described later.

[0036] The iodine value of the rosins is, for example, 0 to 200, preferably 0 to 100. More specifically, from the viewpoint of improving workability, the iodine value of the rosins is, for example, 200 or less, preferably 100 or less. The iodine value of the rosins is, for example, 0 or more. The iodine value of the rosins is measured in accordance with JIS K 0070 (1992).

[0037] Fatty acids are acids that do not have a ring structure. Examples of fatty acids include fatty acids having 2 to 30 carbon atoms, and preferably fatty acids having 10 to 25 carbon atoms. More specifically, examples of fatty acids include saturated fatty acids and unsaturated fatty acids.

[0038] Examples of saturated fatty acids include saturated fatty acids having 2 to 30 carbon atoms. More specific examples of saturated fatty acids include octylic acid, isostearic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, and melissic acid. These can be used alone or in combination of two or more.

[0039] Examples of unsaturated fatty acids include unsaturated fatty acids having 2 to 30 carbon atoms. More specific examples of unsaturated fatty acids include palmitoleic acid, oleic acid, elaidic acid, erucic acid, linoleic acid, linolenic acid, gadoleic acid, and arachidonic acid. These can be used alone or in combination of two or more types.

[0040] Further, examples of fatty acids include fatty acids derived from animals and plants. Examples of fatty acids derived from animals and plants include plant-derived fatty acids and animal-derived fatty acids. More specific examples of plant-derived fatty acids include coconut fatty acids, rice bran fatty acids, castor oil fatty acids, safflower oil fatty acids, linseed oil fatty acids, tung oil fatty acids, soybean oil fatty acids, sesame oil fatty acids, poppy seed oil fatty acids, perilla oil fatty acids, hemp seed oil fatty acids, grape kernel oil fatty acids, corn oil fatty acids, tall oil fatty acids, sunflower oil fatty acids, cottonseed oil fatty acids, and walnut oil fatty acids. Examples of animal-derived fatty acids include beef tallow fatty acids, lard fatty acids, and fish oil fatty acids. These can be used alone or in combination of two or more.

[0041] The fatty acids can be used alone or in combination of two or more. The fatty acids are appropriately selected depending on the purpose and application.

[0042] For example, from the viewpoint of environmental friendliness, fatty acids derived from animals and plants are preferred, fatty acids derived from plants are more preferred, and tall oil fatty acids and coconut oil fatty acids are even more preferred. By using fatty acids derived from animals and plants, a rubber additive having an excellent biomass content can be obtained.

[0043] From the viewpoint of mechanical strength, the fatty acids are preferably saturated fatty acids having 2 to 30 carbon atoms, and more preferably stearic acid.

[0044] The iodine value of the fatty acids is, for example, 0 to 200, more preferably 0 to 170, even more preferably 0 to 140, even more preferably 0 to 100, even more preferably 0 to 45, and particularly preferably 0 to 15. More specifically, from the viewpoint of mechanical strength, the iodine value of the fatty acids is, for example, 200 or less, preferably 170 or less, even more preferably 140 or less, even more preferably 100 or less, even more preferably 45 or less, and particularly preferably 15 or less. The iodine value of the fatty acids is, for example, 0 or more. The iodine value of the fatty acids is measured in accordance with JIS K 0070 (1992) as described in the examples below. The iodine value of the fatty acids can also be calculated from the molecular structure of the fatty acids identified by confirming peaks derived from the fatty acids by pyrolysis GCMS analysis as described in the examples below.

[0045] The ratio of rosins and fatty acids used in combination is appropriately set depending on the desired physical properties. More specifically, the content of rosins is, for example, 10 to 90 moles, preferably 20 to 90 moles, more preferably 30 to 90 moles, even more preferably 35 to 80 moles, and particularly preferably 40 to 60 moles, per 100 moles of the total of rosins and fatty acids. Furthermore, the content of fatty acids is, for example, 10 to 90 moles, preferably 10 to 80 moles, more preferably 10 to 70 moles, even more preferably 20 to 65 moles, and particularly preferably 40 to 60 moles, per 100 moles of the total of rosins and fatty acids.

[0046] In particular, from the viewpoint of wet grip performance, it is preferable that the rosin content be relatively high and the fatty acid content be relatively low. For example, the lower limit of the rosin content is preferably 30 moles or more, more preferably 35 moles or more, even more preferably 40 moles or more, even more preferably 60 moles or more, and particularly preferably 80 moles or more, per 100 moles of the total of rosins and fatty acids. Furthermore, the upper limit of the fatty acid content is preferably 70 moles or less, more preferably 65 moles or less, even more preferably 60 moles or less, even more preferably 40 moles or less, and particularly preferably 20 moles or less, per 100 moles of the total of rosins and fatty acids.

[0047] On the other hand, from the viewpoint of low viscosity, the rosin content is preferably relatively low and the fatty acid content is relatively high. For example, the upper limit of the rosin content is preferably 90 moles or less, more preferably 80 moles or less, even more preferably 60 moles or less, and even more preferably 40 moles or less, per 100 moles of the total of rosins and fatty acids. Furthermore, the lower limit of the fatty acid content is preferably 10 moles or more, more preferably 20 moles or more, even more preferably 40 moles or more, per 100 moles of the total of rosins and fatty acids.

[0048] Although details will be described later, there are no particular limitations on the form in which the rosins and fatty acids are used in combination in the carboxyl group-containing component.

[0049] For example, the rosins and fatty acids may be mixed in the above ratio by a known method and used.

[0050] Also, for example, the rosins and fatty acids may be prepared in the above ratios and used separately without being mixed.

[0051] Alternatively, the rosins and fatty acids may be used without being mixed, for example, as a composition containing the rosins and fatty acids in the above-mentioned ratios from the beginning (hereinafter, referred to as a "combined composition"). An example of a combined composition is tall oil. Tall oil contains, for example, tall oil rosin and tall oil fatty acids in the above-mentioned ratios.

[0052] [Alcohol Component] The alcohol component contains a trihydric or higher alcohol. The alcohol component preferably consists of a trihydric or higher alcohol.

[0053] Examples of trihydric or higher alcohols include trihydric alcohols, tetrahydric alcohols, pentahydric alcohols, and hexahydric or higher alcohols. Examples of trihydric alcohols include glycerin, trimethylolpropane, trimethylolethane, and triethylolethane. Examples of tetrahydric alcohols include pentaerythritol. Examples of pentahydric alcohols include pentahydric polyglycerin (triglycerin), adonitol, arabitol, and xylitol. Examples of hexahydric or higher alcohols include dipentaerythritol, sorbitol, mannitol, heptahydric polyglycerin (pentaglycerin), and nonahydric polyglycerin (heptaglycerin). These may be used alone or in combination of two or more. From the viewpoints of wet grip properties and low viscosity, trihydric alcohols are preferred, and glycerin is more preferred. Furthermore, from the viewpoint of improving the biomass content, alcohols derived from animals and plants are preferred, specifically glycerin.

[0054] The alcohol component can contain a monohydric alcohol and / or a dihydric alcohol.

[0055] Examples of monohydric alcohols include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, s-butanol, t-butanol, pentanol, neopentanol, hexanol, octanol, and 2-ethylhexanol. Examples of dihydric alcohols include ethylene glycol, propylene glycol, neopentyl glycol, trimethylene glycol, tetramethylene glycol, 1,3-butanediol, and 1,6-hexanediol. These can be used alone or in combination of two or more.

[0056] The content ratio of the monohydric alcohol and / or dihydric alcohol is appropriately set within a range that does not impair the excellent effects of the present invention. The content ratio of the monohydric alcohol and / or dihydric alcohol is, for example, 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 0% by mass, based on the total amount of the alcohol components. In other words, particularly preferably, the alcohol components do not contain monohydric alcohols or dihydric alcohols, and consist only of trihydric or higher alcohols.

[0057] [Esterification Reaction] In the esterification reaction, a carboxyl group-containing component is reacted with an alcohol component. The method for reacting the carboxyl group-containing component with the alcohol component is not particularly limited.

[0058] For example, a carboxyl group-containing component containing rosins and fatty acids can be reacted in a lump with an alcohol component containing a trivalent or higher alcohol. That is, the rosins and fatty acids are premixed in the above ratio (primary mixing), and then the resulting mixed composition is mixed with an alcohol component (secondary mixing) to carry out an esterification reaction. Alternatively, for example, the rosins, fatty acids, and alcohol component can be mixed together (lump mixing) without premixing the rosins and fatty acids, and then reacted. Alternatively, for example, a composition (tall oil) that originally contains both rosins and fatty acids can be mixed with an alcohol component (secondary mixing) to carry out an esterification reaction.

[0059] In such cases, the mixing ratio of the carboxy group-containing component and the alcohol component is adjusted based on the equivalent ratio (OH / COOH) of the hydroxyl groups (OH) in the alcohol component (alcohols with a valence of 3 or more) to the carboxyl groups (COOH) in the carboxy group-containing component (rosins and fatty acids). Preferably, the equivalent ratio is adjusted so that the hydroxyl groups (OH) in the alcohol component are in excess of the carboxyl groups (COOH) in the carboxy group-containing component.

[0060] More specifically, the equivalent ratio (OH / COOH) of the hydroxyl groups (OH) in the alcohol component to the carboxyl groups (COOH) in the carboxyl group-containing component is, for example, 0.9 to 3.5, preferably 0.9 to 2.0, more preferably 1.0 to 1.8, even more preferably 1.1 to 1.5, and particularly preferably 1.2 to 1.3.

[0061] The reaction conditions are appropriately set. The reaction temperature is, for example, 150 to 350° C., preferably 200 to 300° C. The reaction time is 1 to 24 hours, preferably 3 to 12 hours.

[0062] The esterification reaction produces an ester compound as a reaction product between the carboxyl group-containing component and the alcohol component. In this case, the ester compound contains a collective reaction product of the rosin, the fatty acid, and the alcohol component.

[0063] More specifically, in the above reaction, due to the difference in the stereostructure between the fatty acids and the rosin, the fatty acids and the alcohol component first undergo ester condensation to form an ester group, resulting in a fatty acid ester compound as the reaction product of the fatty acids and the alcohol component.

[0064] In the above reaction, the alcohol component contains a trivalent or higher alcohol, and preferably consists of a trivalent or higher alcohol, and therefore the fatty acid ester compound contains a fatty acid ester compound having three or more ester bonds in one molecule, and preferably consists of a fatty acid ester compound having three or more ester bonds in one molecule.

[0065] Once a certain amount of fatty acid ester compound is produced, the rosin and the alcohol component undergo ester condensation to form an ester group, resulting in a rosin ester compound as a reaction product of the rosin and the alcohol component.

[0066] In the above reaction, the alcohol component contains, and preferably consists of, a trivalent or higher alcohol, and therefore the rosin ester compound contains, and preferably consists of, a rosin ester compound having three or more ester bonds per molecule.

[0067] As described above, the batch reaction of rosins and fatty acids with the alcohol component produces a rosin-based ester compound having three or more ester bonds per molecule and a fatty acid-based ester compound having three or more ester bonds per molecule. As a result, the ester compound is obtained as the batch reaction product of the rosins, fatty acids, and the alcohol component.

[0068] Hereinafter, the product of the simultaneous reaction of rosins, fatty acids, and an alcohol component will be referred to as a rosin-fatty acid ester compound.

[0069] The rosin-fatty acid ester compound is an ester composition containing the above-mentioned rosin ester compound and the above-mentioned fatty acid ester compound. The rosin-fatty acid ester compound may further contain by-products.

[0070] Examples of the by-products include ester compounds obtained by esterification reaction of both fatty acids and rosins with one molecule of a trivalent or higher alcohol (i.e., ester compounds obtained by reaction of one or more molecules of fatty acids and one or more molecules of rosins with one molecule of a trivalent or higher alcohol). The content of the by-products is appropriately set within a range that does not impair the excellent effects of the present invention.

[0071] The rosin-fatty acid ester compound is contained in the reaction product liquid in the above reaction. The reaction product liquid is purified by a known method, if necessary. Examples of purification include removal of unreacted raw materials and removal of solvents. Examples of purification methods include distillation and extraction.

[0072] The progress of the esterification reaction is confirmed, for example, based on the acid value. The upper limit of the acid value of the rosin-fatty acid ester compound is, for example, 30 mg KOH / g or less, preferably 25 mg KOH / g or less. The lower limit of the acid value of the ester compound is not particularly limited, and is, for example, 0 mg KOH / g or more.

[0073] The method for reacting the carboxyl group-containing component with the alcohol component is not limited to the above. For example, the rosin and the fatty acid may be used separately without being mixed.

[0074] More specifically, for example, a rosin-based ester compound can be obtained by ester condensation of only rosins with an alcohol component without mixing rosins with fatty acids. Also, a fatty acid-based ester compound can be obtained by ester condensation of only fatty acids with an alcohol component without mixing rosins with fatty acids. In other words, the rosin-based ester compound and the fatty acid-based ester compound can be obtained separately.

[0075] In this method, for example, a rosin-based ester compound and a fatty acid-based ester compound can be mixed to obtain an ester compound as a mixture of these. That is, the ester compound may be a mixture of a reaction product of a rosin with a trihydric or higher alcohol and a reaction product of a fatty acid with a trihydric or higher alcohol. In other words, the ester compound may be a mixed composition containing a rosin-based ester compound obtained separately and a fatty acid-based ester compound obtained separately.

[0076] More specifically, in this method, first, the rosin alone is subjected to an esterification reaction with an alcohol component.

[0077] In such cases, the mixing ratio of the rosin and the alcohol component is adjusted based on the equivalent ratio (OH / COOH) of the hydroxyl groups (OH) in the alcohol component to the carboxyl groups (COOH) in the rosin, preferably such that the hydroxyl groups (OH) in the alcohol component are in excess relative to the carboxyl groups (COOH) in the rosin.

[0078] More specifically, the equivalent ratio (OH / COOH) of hydroxyl groups (OH) in the alcohol component to carboxyl groups (COOH) in the rosin is, for example, 0.9 to 3.5, preferably 0.9 to 2.0, more preferably 1.0 to 1.8, even more preferably 1.1 to 1.5, and particularly preferably 1.2 to 1.3.

[0079] The reaction conditions are appropriately set. The reaction temperature is, for example, 150 to 350° C., preferably 200 to 300° C. The reaction time is 1 to 24 hours, preferably 3 to 12 hours.

[0080] Then, by the above esterification reaction, a rosin-based ester compound is obtained as a reaction product between the rosin and the alcohol component.

[0081] In the above reaction, the carboxy group-containing component contains rosins. Therefore, the rosin-based ester compound has an ester group formed by ester condensation between rosins and an alcohol component. Furthermore, in the above reaction, the alcohol component contains a trihydric or higher alcohol, preferably a trihydric or higher alcohol. Therefore, the rosin-based ester compound contains a rosin-based ester compound having three or more ester bonds per molecule, preferably a rosin-based ester compound having three or more ester bonds per molecule.

[0082] The rosin-based ester compound is contained in the reaction product liquid in the above reaction. The reaction product liquid is purified by a known method, if necessary. Examples of purification include removal of unreacted raw materials and removal of solvents. Examples of purification methods include distillation and extraction.

[0083] The progress of the rosin-based esterification reaction is confirmed, for example, based on the acid value. The upper limit of the acid value of the rosin-based ester compound is, for example, 30 mg KOH / g or less, preferably 25 mg KOH / g or less. The lower limit of the acid value of the rosin-based ester compound is not particularly limited, and is, for example, 0 mg KOH / g or more.

[0084] On the other hand, in this method, separately from the above, only fatty acids are subjected to an esterification reaction with an alcohol component.

[0085] In such cases, the mixing ratio of the fatty acids and the alcohol component is adjusted based on the equivalent ratio (OH / COOH) of the hydroxyl groups (OH) in the alcohol component to the carboxyl groups (COOH) in the fatty acids. Preferably, the equivalent ratio is adjusted so that the hydroxyl groups (OH) in the alcohol component are in excess relative to the carboxyl groups (COOH) in the fatty acids.

[0086] More specifically, the equivalent ratio (OH / COOH) of the hydroxyl groups (OH) in the alcohol component to the carboxyl groups (COOH) in the fatty acids is, for example, 0.9 to 3.5, preferably 0.9 to 2.0, more preferably 1.0 to 1.8, even more preferably 1.1 to 1.5, and particularly preferably 1.2 to 1.3.

[0087] The reaction conditions are appropriately set. The reaction temperature is, for example, 150 to 350° C., preferably 200 to 300° C. The reaction time is 1 to 24 hours, preferably 3 to 12 hours.

[0088] Then, by the above esterification reaction, a fatty acid ester compound is obtained as a reaction product between the fatty acid and the alcohol component.

[0089] In the above reaction, the carboxy group-containing component contains a fatty acid. Therefore, the fatty acid ester compound has an ester group formed by ester condensation between a fatty acid and an alcohol component. Furthermore, in the above reaction, the alcohol component contains a trihydric or higher alcohol, preferably a trihydric or higher alcohol. Therefore, the fatty acid ester compound contains a fatty acid ester compound having three or more ester bonds per molecule, preferably a fatty acid ester compound having three or more ester bonds per molecule.

[0090] The fatty acid ester compound is contained in the reaction product liquid in the above reaction. The reaction product liquid is purified by a known method, if necessary. Examples of purification include removal of unreacted raw materials and removal of solvents. Examples of purification methods include distillation and extraction.

[0091] The progress of the fatty acid esterification reaction is confirmed, for example, based on the acid value. The upper limit of the acid value of the fatty acid ester compound is, for example, 30 mg KOH / g or less, preferably 25 mg KOH / g or less. The lower limit of the acid value of the fatty acid ester compound is not particularly limited, and is, for example, 0 mg KOH / g or more.

[0092] In this method, the rosin ester compound and the fatty acid ester compound are then mixed together in a mixing ratio adjusted so that the ratio of the rosins used in the production of the rosin ester compound to the fatty acids used in the production of the fatty acid ester compound falls within the above range.

[0093] The method and timing of mixing the rosin ester compound and the fatty acid ester compound are not particularly limited. For example, the rosin ester compound and the fatty acid ester compound may be mixed in advance before using the rubber additive. Alternatively, for example, when using the rubber additive, the rosin ester compound and the fatty acid ester compound may be added separately to a rubber component (described later), and the rosin ester compound and the fatty acid ester compound may be mixed in the rubber component (described later).

[0094] The rosin ester compound and the fatty acid ester compound are mixed to obtain an ester compound. That is, the ester compound can contain a rosin ester compound and a fatty acid ester compound.

[0095] Furthermore, the ester compound can contain a rosin-fatty acid ester compound, an individually obtained rosin ester compound, and / or an individually obtained fatty acid ester compound. More specifically, the ester compound can contain three types: a rosin-fatty acid ester compound, an individually obtained rosin ester compound, and an individually obtained fatty acid ester compound. Alternatively, the ester compound can contain two types: a rosin-fatty acid ester compound and an individually obtained rosin ester compound. Alternatively, the ester compound can contain two types: a rosin-fatty acid compound and an individually obtained fatty acid ester compound.

[0096] In such a case, the mixing ratio of each compound is adjusted so that the ratio of the rosins used in the respective production and the fatty acids used in the respective production falls within the above range.

[0097] In the rubber additive, the ester compound is not limited to the above-mentioned ester compound (i.e., the reaction product of a carboxyl group-containing component and an alcohol component). For example, the ester compound may contain fats and oils as a fatty acid-based ester compound.

[0098] That is, the ester compound may contain a rosin-based ester compound as a reaction product of a carboxyl group-containing component and an alcohol component, and a fat or oil. In other words, a fat or oil may be used as the fatty acid-based ester compound instead of the reaction product of a fatty acid and an alcohol component.

[0099] In such cases, the rosin-based ester compound contains, for example, a rosin-based ester compound as a reaction product of a carboxyl group-containing component and an alcohol component. That is, the rosin-based ester compound contains, for example, a reaction product of a carboxyl group-containing component containing the above-mentioned rosins with the above-mentioned alcohol component. The abietadienoic acid content and iodine value of the rosins are as described above.

[0100] Examples of fats and oils include palm oil, linseed oil, yuzu oil, pistachio oil, rice oil, safflower oil, apricot oil, cottonseed oil, sesame oil, corn oil, watermelon oil, soybean oil, poppy seed oil, apple oil, sunflower oil, cactus oil, tall oil, walnut oil, tung oil, clove oil, and castor oil. These can be used alone or in combination of two or more. Fat and oils can be obtained, for example, as commercially available products. Fat and oils can also be produced by known methods using, for example, glycerol 3-phosphate and fatty acids as raw materials.

[0101] Fats and oils contain molecular structures derived from fatty acids (hereinafter referred to as fatty acid structures). Examples of fatty acids that form the fatty acid structures of fats and oils (hereinafter referred to as raw fatty acids) include the fatty acids described above.

[0102] The iodine value of the raw material fatty acids is, for example, 0 to 200, more preferably 0 to 170, even more preferably 0 to 140, even more preferably 0 to 100, even more preferably 0 to 45, and particularly preferably 0 to 15. More specifically, from the viewpoint of mechanical strength, the iodine value of the raw material fatty acids is, for example, 200 or less, preferably 170 or less, even more preferably 140 or less, even more preferably 100 or less, even more preferably 45 or less, and particularly preferably 15 or less. The iodine value of the raw material fatty acids is, for example, 0 or more. The iodine value of the raw material fatty acids is measured in accordance with JIS K 0070 (1992) as described in the Examples below. The iodine value of the raw material fatty acids can also be calculated from the molecular structure of the fatty acids identified by pyrolysis GCMS analysis, as described in the Examples below. The iodine value of the raw material fatty acids for the fatty acid ester compound as the reaction product can also be calculated using the same method as above.

[0103] Furthermore, the ester compound may contain, in addition to the rosin-based ester compound and the oil-and-fat, a fatty acid-based ester compound as a reaction product of a carboxyl group-containing component and an alcohol component. In other words, the fatty acid-based ester compound may be a combination of an oil-and-fat and a reaction product of a fatty acid and an alcohol component.

[0104] In such a case, the fatty acid ester compound as the reaction product can be obtained, for example, by reacting the carboxyl group-containing component containing the above-mentioned fatty acid with the above-mentioned alcohol component by the above-mentioned method. The iodine value of the fatty acid is as described above.

[0105] When the fat or oil and the fatty acid ester compound as a reaction product are used in combination, the ratio of these to be used in combination is appropriately set depending on the purpose and application.

[0106] [Esterification Catalyst] In the above esterification reaction, an esterification catalyst is added at an appropriate timing as necessary. In such a case, the rubber additive can further contain an esterification catalyst in addition to the above ester compound.

[0107] Examples of esterification catalysts include metal catalysts and non-metal catalysts. Metal catalysts include magnesium oxide, antimony trioxide, dibutyltin oxide, tetrabutyl titanate, tetrabutyl zirconate, and zinc acetate. Non-metal catalysts include paratoluenesulfonic acid and stearyltrimethylammonium chloride. These catalysts can be used alone or in combination of two or more.

[0108] The content of the esterification catalyst is set depending on the type and amount of the carboxy group-containing component and the type and amount of the alcohol component. For example, the amount of the esterification catalyst is, for example, 0.01 to 1.0 mass%, preferably 0.1 to 0.5 mass%, relative to the total amount of the carboxy group-containing component, the alcohol component, and the esterification catalyst.

[0109] [Additives] The rubber additive may further contain additives as long as it contains the above-mentioned ester compound. Examples of additives include known additives such as dispersants, vulcanization accelerators, reinforcing materials, antioxidants, anti-degradants, crack inhibitors, silane coupling agents, vulcanization retarders, vulcanization activators, plasticizers, softeners, oils, and fillers. These additives may be used alone or in combination of two or more. The content ratio of the additives is appropriately set within a range that does not impair the excellent effects of the present invention.

[0110] [Effects] In the rubber additive, the ester compound contains a rosin-based ester compound having three or more ester bonds in one molecule and a fatty acid-based ester compound having three or more ester bonds in one molecule. Therefore, the rubber composition has excellent low viscosity, and a molded product has excellent wet grip properties.

[0111] 2. Rubber Composition The rubber composition is a mixture of rubber raw material compounds. The rubber composition contains a known rubber component as the rubber raw material compound and the above-mentioned rubber additives.

[0112] [Rubber Component] The rubber component is not particularly limited, and examples thereof include diene rubbers. Examples of diene rubbers include natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile butadiene rubber (NBR), ethylene propylene diene rubber (EPDM), and chloroprene rubber (CR). These can be used alone or in combination of two or more. Preferred examples include natural rubber (NR), styrene butadiene rubber (SBR), and butadiene rubber (BR), and more preferred examples include a combination of styrene butadiene rubber (SBR) and butadiene rubber (BR). When styrene butadiene rubber (SBR) and butadiene rubber (BR) are used in combination, the ratio of their use is appropriately set depending on the purpose and application.

[0113] [Rubber Additive] The rubber additive contains the above-mentioned ester compound. Preferably, the rubber additive consists of an ester compound. As described above, the ester compound can contain a rosin-fatty acid ester compound (bulk reaction product). The ester compound can also contain an individually obtained rosin ester compound and an individually obtained fatty acid ester compound. Furthermore, the ester compound can also contain a rosin-fatty acid ester compound (bulk reaction product), an individually obtained rosin ester compound, and / or an individually obtained fatty acid ester compound.

[0114] The timing of adding the rubber additive is not particularly limited. For example, the rubber additive may be added directly to the rubber component. Alternatively, the rubber additive may be added to raw material components in the synthesis of the rubber component, and the rubber component may be produced while a composition containing the rubber additive and the rubber component is being produced.

[0115] The method for adding the rubber additives is not particularly limited. For example, a rosin-fatty acid ester compound may be added. Alternatively, a rosin ester compound and a fatty acid ester compound may be premixed and the mixture may be added. Furthermore, the rosin ester compound and the fatty acid ester compound may be added separately without being mixed.

[0116] Preferably, a rosin-fatty acid ester compound is added, or a rosin-based ester compound and a fatty acid ester compound are mixed in advance and the mixture is added, more preferably, a rosin-fatty acid ester compound is added.

[0117] The amount of the rubber additive added is appropriately set depending on the purpose and application. For example, the amount of the rubber additive is, for example, 0.1 to 50 parts by mass, preferably 1 to 30 parts by mass, per 100 parts by mass of the rubber component.

[0118] [Other Compounds] The rubber composition may contain other compounds as rubber raw material compounds. The other compounds are components other than the above-mentioned rubber components and rubber additives. Examples of the other compounds include vulcanizing agents, vulcanization accelerators, and fillers.

[0119] An example of the vulcanizing agent is sulfur. The sulfur is not particularly limited, but examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. These can be used alone or in combination of two or more. The blending ratio of the vulcanizing agent is, for example, 0.5 to 5 parts by mass, or preferably 1 to 3 parts by mass, per 100 parts by mass of the rubber component.

[0120] Examples of vulcanization accelerators include zinc oxide, stearic acid, sulfenamide vulcanization accelerators, and guanidine vulcanization accelerators. Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), and N,N-diisopropyl-2-benzothiazolesulfenamide. Examples of guanidine vulcanization accelerators include diphenylguanidine (DPG), di-orthotriguanidine, triphenylguanidine, orthotolylbiguanide, and diphenylguanidine phthalate. These can be used alone or in combination of two or more. The blending ratio of the vulcanization accelerators is appropriately determined depending on the purpose and application.

[0121] Examples of fillers include inorganic fillers and organic fillers. Examples of inorganic fillers include calcium carbonate, magnesium carbonate, silicic acid and its salts, silica, clay, talc, mica powder, bentonite, alumina, aluminum silicate, carbon (acetylene black, etc.), and aluminum powder. Examples of organic fillers include cork. These can be used alone or in combination of two or more. The blending ratio of the fillers is appropriately set depending on the purpose and application.

[0122] Furthermore, the rubber composition may contain known additives as rubber raw material compounds in appropriate proportions, as needed. Examples of the additives include anti-aging agents, anti-cracking agents, silane coupling agents, vulcanization aids, vulcanization retarders, vulcanization activators, plasticizers, softeners, and antioxidants. Examples of the anti-aging agents include antiozonants, heat-degrading agents, and oxidation-degrading agents. Known additives may be blended in advance with at least one of the above components, or may be blended simultaneously with the components during their mixing.

[0123] [Production of Rubber Composition] The rubber composition is prepared by mixing the above-mentioned rubber raw material compounds by a known method. The mixing method is not particularly limited, and a known kneading machine is used. Examples of the kneading machine include a roll, a Banbury mixer, and a kneader.

[0124] The mixing order and mixing conditions are not particularly limited and are set appropriately depending on the equipment used, etc. As described above, the mixing form of the rubber additives in mixing the rubber composition is not particularly limited. That is, the rosin-fatty acid ester compound may be added to and mixed with the rubber component. Also, for example, a mixture of the rosin ester compound and the fatty acid ester compound may be added to and mixed with the rubber component. Also, for example, the rosin ester compound and the fatty acid ester compound may be added to and mixed with the rubber component separately.

[0125] [Effects] The rubber composition as described above has excellent low viscosity due to the inclusion of the rubber additives, and can also be used to obtain molded articles with excellent wet grip properties.

[0126] 3. Molded Product The molded product is not particularly limited, and examples thereof include known rubber molded products. Examples of the rubber molded product include tires, sealing materials, insulating materials, vibration-proof materials, and sound-proofing materials, and preferably tires. That is, the tire preferably contains a molded product of the above-mentioned rubber composition, and more preferably is a molded product of the above-mentioned rubber composition.

[0127] The method for producing a tire using the above-mentioned rubber composition is not particularly limited, and a known vulcanization molding method can be used. In this method, for example, first, the rubber composition (unvulcanized state) is molded to obtain an unvulcanized tread. If necessary, other tire components can be laminated to the unvulcanized tread. Examples of other tire components include a sidewall portion, a shoulder portion, a bead portion, and an inner liner. Next, the unvulcanized tread laminated to other tire components, if necessary, is heated and pressurized in a vulcanizer to be vulcanized. As a result, the rubber composition is vulcanized, and a tire is obtained as a molded product.

[0128] [Operation and Effect] The tire described above contains a molded product of the rubber composition described above, and therefore has excellent productivity and excellent wet grip properties.

[0129] Therefore, the tire is preferably used as a vehicle tire and an aircraft tire, and more preferably used as a vehicle tire. Examples of vehicles include automobiles, motorcycles, and railroad vehicles.

[0130] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Note that "parts" and "%" are by mass unless otherwise specified. Furthermore, specific numerical values ​​such as blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be substituted with the corresponding upper limit values ​​(numeric values ​​defined as "equal to or less than") or lower limit values ​​(numeric values ​​defined as "equal to or more than" or "exceeding") of the blending ratios (content ratios), physical property values, parameters, etc. described in the above "Modes for Carrying Out the Invention."

[0131] 1. Raw materials The following raw materials were prepared:

[0132] 1-1. Rubber additives

[0133] [Rosins] (1) Tall oil rosin: abbreviated as TR, acid value 170 mg KOH / g, trade name: Hartall R-WW, manufactured by Harima Chemicals (2) Gum rosin: abbreviated as GR, acid value 170 mg KOH / g, trade name: Massoniana Gum Rosin X, manufactured by LONG TAN LANG SON (3) Disproportionated gum rosin: acid value 170 mg KOH / g, trade name: G100F, manufactured by Harima Chemicals

[0134] [Fatty acids] (1) Tall oil fatty acid: abbreviated as TOFA, acid value 200 mg KOH / g, trade name: FA-1, manufactured by Harima Chemicals (2) Palm fatty acid: acid value 267 mg KOH / g, trade name: Palm Fatty Acid DC, manufactured by New Japan Chemical (3) Stearic acid: acid value 200 mg KOH / g, trade name: EDENOR C18-98, manufactured by Maruzen Pharmaceuticals (4) Linoleic acid: acid value 200 mg KOH / g, trade name: Linoleic acid, manufactured by Fujifilm Wako Pure Chemical Industries

[0135] [Alcohols] (1) Diethylene glycol: dihydric alcohol (2) 2-ethylhexanol: monohydric alcohol (3) Glycerin: trihydric alcohol (4) Polyglycerin: pentahydric alcohol, trade name R-PG, manufactured by Sakamoto Pharmaceutical Industry Co., Ltd.

[0136] [Oils and Fats] (1) Palm oil: acid value 0 mg KOH / g, trade name: RBD PKO, manufactured by Wilmar

[0137] 1-2. Rubber composition (1) BR: Polybutadiene rubber, trade name BR01, manufactured by JSR (2) SBR: Styrene butadiene rubber, trade name HPR850, manufactured by JSR (3) Silica: Inorganic filler, trade name Nipsil AQ, manufactured by Tosoh Silica (4) Antidegradant: Antiozonant, trade name Ozonone 6C, manufactured by Seiko Chemical (5) Zinc oxide: Vulcanization accelerator, trade name Zinc Oxide, manufactured by Seido Chemical Industry (6) Stearic acid: Vulcanization accelerator, trade name Tsubaki Stearate, manufactured by NOF Corp. (7) Silane coupling agent: Trade name Si75, manufactured by Evonik (8) Sulfur: Vulcanizing agent, trade name Oil Sulfur, manufactured by Hosoi Chemical Industry Co., Ltd. (9) Vulcanization accelerator 1: Sulfenamide-based vulcanization accelerator, trade name CZ, manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (10) Vulcanization accelerator 2: Guanidine-based vulcanization accelerator, trade name Soxinol D / DG, manufactured by Sumitomo Chemical

[0138] 2. Measurement of Physical Properties (1) Content of Abietadienoic Acid The content of abietadienoic acid relative to the total amount of rosins was calculated by the following method.

[0139] That is, rosins were analyzed by GCMS under the following conditions, and a peak derived from abietic acid, a peak derived from palustric acid, and a peak derived from neoabietic acid were confirmed.

[0140] More specifically, each component has a characteristic fragment peak, and each component was identified from the fragment peak as follows.

[0141] Abietic acid: peaks at which fragment peaks 213, 256, and 316 were detected. Palustric acid: peaks at which the ratio of fragment peaks 241 and 301 was 1:1. Neoabietic acid: peaks at which fragment peaks 135 and 316 were detected.

[0142] The ratio of the peak area of ​​the peak derived from abietic acid to the total peak area (hereinafter referred to as "abietic acid peak area ratio") was calculated. The abietic acid peak area ratio indicates the content ratio of abietic acid to the total amount of rosins.

[0143] The ratio of the peak area of ​​the peak derived from parastolic acid to the total peak area (hereinafter referred to as the parastolic acid peak area ratio) was also calculated. The parastolic acid peak area ratio indicates the content of parastolic acid relative to the total amount of rosins.

[0144] Furthermore, the ratio of the peak area of ​​the peak attributable to neoabietic acid to the total peak area (hereinafter referred to as neoabietic acid peak area ratio) was calculated. The neoabietic acid peak area ratio indicates the content ratio of neoabietic acid to the total amount of rosins.

[0145] The sum of the peak area ratios of abietic acid, palustric acid, and neoabietic acid was calculated, and the sum of the peak area ratios of abietic acid, palustric acid, and neoabietic acid was calculated as the content of abietadienoic acid relative to the total amount of rosins.

[0146] <GCMS Measurement> Apparatus: Gas chromatograph mass spectrometry (GC-MS), Shimadzu Corporation GCMS-TQ8030 Column: DB-5 Measurement conditions: Hold at 150°C for 2 minutes, then heat from 150°C to 250°C at a rate of 4°C / min, and then heat from 250°C to 325°C at a rate of 20°C / min to remove high-boiling point components. Injection port / FID: 265°C Split ratio: 10 Helium flow rate: 1 ml / min

[0147] (2) Iodine Value of Fatty Acids The iodine value of fatty acids used as raw materials in the production of fatty acid ester compounds was measured in accordance with JIS K0070 (1992).

[0148] Specifically, 3.0 g to 0.1 g of fatty acids were dissolved in approximately 10 mL of hexane to obtain a hexane solution of fatty acids. Next, 25 mL of Wiess reagent (manufactured by Kanto Chemical Co., Ltd.) was added to the hexane solution of fatty acids, and the mixture was allowed to stand in a dark place for 30 minutes to 1 hour to allow the fatty acids to react with the Wiess reagent, thereby obtaining a test solution.

[0149] Next, about 20 mL of potassium iodide and about 100 mL of pure water were added to the test solution, and then the test solution was titrated with a sodium thiosulfate solution (concentration: 0.1 mol / L, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0150] When the test solution turned pale yellow, several drops of a 1% starch solution were added to the test solution to turn it blue, and the test solution was then titrated with a sodium thiosulfate solution (concentration: 0.1 mol / L, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) until the blue color disappeared.

[0151] The iodine values ​​of the raw fatty acids of the oils and fats were calculated by the following method. This method also allows the iodine values ​​of the raw fatty acids of the fatty acid ester compounds as reaction products to be calculated.

[0152] Specifically, samples (oils and fats or fatty acid ester compounds as reaction products) were subjected to pyrolysis GCMS analysis under the following conditions, and peaks derived from fatty acids (pure substances) contained in the pyrolysates were confirmed.

[0153] Next, the ratio of the peak area of ​​the peak attributable to each fatty acid (pure substance) to the total peak area of ​​all detected fatty acids was calculated.

[0154] Next, the iodine value of each fatty acid (pure substance) was calculated from the molecular structure, and then the iodine value of the raw fatty acids of the sample (oil or fatty acid ester compound as a reaction product) was calculated from the ratio of the peak area of ​​each fatty acid (pure substance).

[0155] <GCMS Measurement> Apparatus: Gas chromatograph mass spectrometer (GC-MS), Shimadzu Corporation GCMS-TQ8030 Column: DB-5 Pyrolysis furnace: 500°C Measurement conditions: Hold at 160°C for 2 minutes, then increase temperature from 160°C to 320°C at a rate of 4°C / min, then hold at 320°C for 18 minutes. Injection port / FID: 320°C Split ratio: 10 Helium flow rate: 1.3 ml / min

[0156] 3. Production of Rubber Additives and Rubber Compositions Example 1 (1) Rubber Additives Into a four-neck flask equipped with a stirrer, a nitrogen inlet tube, a thermometer, and a Dean-Stark water divider, 119.6 g of tall oil rosin (TR, rosin, acid value 170 mgKOH / g, trade name: Hartall R-WW, manufactured by Harima Chemicals) and 101.5 g of tall oil fatty acid (TOFA, fatty acid, acid value 200 mgKOH / g, trade name: FA-1, manufactured by Harima Chemicals) were placed. The temperature of the contents of the flask was raised to 120°C to dissolve them. The contents of the flask were stirred to homogenize them. This yielded a preliminary mixture.

[0157] Next, 28.9 g of glycerin (a trihydric alcohol) was added to the flask, and the equivalent ratio (OH / COOH) of the hydroxyl groups in the glycerin to the total amount of carboxyl groups in the tall oil rosin and the tall oil fatty acids was 1.3.

[0158] Additionally, 0.3 g of paratoluenesulfonic acid (esterification catalyst) was added to the flask. The temperature of the contents of the flask was then raised to 260°C over 3 hours. The temperature was then maintained at 260°C for 4 hours, allowing the contents of the flask to be esterified. Thereafter, unreacted raw materials (alcohols) were removed from the flask under reduced pressure. As a result, an ester compound (rosin-fatty acid ester compound) was obtained.

[0159] The acid value of the ester compound was measured in accordance with the titration method of JIS K 5601-2-1 (1999) (hereinafter the same). The acid value of the ester compound was 21.5 mg KOH / g. The obtained ester compound was used as a rubber additive.

[0160] In Example 1, the molar ratio (rosins / fatty acids) of the rosins (tall oil rosin, TR) and fatty acids (tall oil fatty acids, TOFA) used in the production of the ester compound was 5 / 5.

[0161] (2) Rubber Composition According to the formulation shown in Table 1, rubber raw materials were prepared and kneaded to produce a rubber composition (unvulcanized). More specifically, all components except the vulcanization accelerator and sulfur were placed in a 74-milliliter internal mixer and kneaded for 6 minutes. The kneaded mixture was then cooled to room temperature. The kneaded mixture was used as a masterbatch. Next, the vulcanization accelerator and sulfur were added to the masterbatch, and the mixture was kneaded for 1.5 minutes in the internal mixer. Next, the kneaded mixture was rolled out using an open roll (manufactured by Toyo Seiki Co., Ltd.). This produced a rubber composition (unvulcanized).

[0162] Examples 2 to 6, Examples 9 to 19, and Comparative Examples 1 to 4: Rosins, fatty acids, and alcohols were reacted together in the same manner as in (1) of Example 1, except for the formulations shown in Tables 2 to 7, to synthesize ester compounds (rosin-fatty acid ester compounds), and rubber additives were obtained. Further, rubber compositions were obtained in the same manner as in (2) of Example 1. The acid values ​​of the ester compounds are shown in Tables 2 to 7.

[0163] Examples 7 and 8 (1) Rubber Additives and Rubber Compositions A rosin-based ester compound (i.e., glycerin ester of tall oil rosin) was obtained in the same manner as in (1) of Example 1, except that tall oil fatty acids were not added, the amount of tall oil rosin was changed to 223.1 g, and the amount of glycerin was changed to 26.9 g. The acid values ​​of the rosin-based ester compounds are shown in Table 2.

[0164] Separately from the above, a fatty acid ester compound (i.e., glycerin ester of tall oil fatty acid) was obtained in the same manner as in (1) of Example 1, except that tall oil rosin was not added, the amount of tall oil fatty acid was changed to 223.6 g, and the amount of glycerin was changed to 26.4 g. The acid value of the fatty acid ester compound is shown in Table 2.

[0165] A mixture of the above rosin-based ester compound (i.e., glycerin ester of tall oil rosin) and the above fatty acid-based ester compound (i.e., glycerin ester of tall oil fatty acid) was used as a rubber additive, and a rubber composition was obtained in the same manner as in (2) of Example 1.

[0166] In Example 7, before kneading the rubber raw material compound, the rosin-based ester compound and the fatty acid-based ester compound were mixed to prepare a rubber additive.

[0167] Furthermore, the rosin ester compound and the fatty acid ester compound were not mixed before kneading the rubber raw material compounds in Example 8. More specifically, the rosin ester compound and the fatty acid ester compound, which were prepared separately as described above, were added separately and mixed together while kneading to prepare the rubber additive.

[0168] In Examples 7 and 8, the blending amounts of the rosin ester compound and the fatty acid ester compound were adjusted so that the molar ratio (rosins / fatty acids) of the rosins (i.e., tall oil rosin) used in the production of the rosin ester compound to the fatty acids (i.e., tall oil fatty acids) used in the production of the fatty acid ester compound was 5 / 5.

[0169] Example 20 (1) Rubber Additive and Rubber Composition 119.6 g of disproportionated gum rosin (rosin, acid value 170 mgKOH / g, product name: G100F, manufactured by Harima Chemicals) was placed in a four-neck flask equipped with a stirrer, a nitrogen inlet tube, a thermometer, and a Dean-Stark water divider. The temperature of the contents of the flask was raised to 120°C to dissolve the contents. The contents of the flask were stirred to homogenize. Next, 14.5 g of glycerin (a trihydric alcohol) was added to the flask. The equivalent ratio (OH / COOH) of the hydroxyl groups in the glycerin to the carboxyl groups in the disproportionated gum rosin was 1.3. 0.1 g of paratoluenesulfonic acid (esterification catalyst) was added to the flask. The temperature of the contents of the flask was then raised to 270°C over 3 hours. The temperature was maintained at 270°C for 4 hours to esterify the contents of the flask. Thereafter, unreacted raw materials (alcohols) were removed from the flask under reduced pressure. This resulted in a rosin-based ester compound (i.e., a glycerin ester of disproportionated gum rosin). The acid value of the rosin-based ester compound is shown in Table 7.

[0170] Separately from the above, coconut oil (acid value 0 mgKOH / g, trade name: RBD PKO, manufactured by Wilmar) was prepared as a fatty acid ester compound.

[0171] A mixture of the above rosin-based ester compound (i.e., glycerin ester of disproportionated gum rosin) and the above fatty acid-based ester compound (i.e., coconut oil) was used as a rubber additive, and a rubber composition was obtained in the same manner as in (2) of Example 1.

[0172] In Example 20, before kneading the rubber raw material compound, the rosin-based ester compound and the fatty acid-based ester compound were mixed to prepare a rubber additive.

[0173] In Example 20, the blending amounts of the rosin-based ester compound and the fatty acid-based ester compound were adjusted so that the molar ratio (rosins / fatty acids) of the rosins (i.e., disproportionated gum rosin) used in the production of the rosin-based ester compound to units derived from fatty acids contained in coconut oil (hereinafter, referred to as fatty acids) was 5 / 5.

[0174] 4. Evaluation (1) Wet Grip Property (tan δ (0°C), Dynamic Viscoelasticity Measurement) First, the vulcanization time of the above rubber composition (unvulcanized) was calculated using a rotorless rheometer (manufactured by Toyo Seiki Seisakusho, Ltd.) The vulcanization time was calculated as twice the T95 value.

[0175] Next, the above rubber composition (unvulcanized) was vulcanized in a mold (10.5 cm × 10.5 cm × 0.2 cm) at 160°C to obtain a vulcanized rubber. Thereafter, the dynamic viscoelasticity of the vulcanized rubber was measured under the following conditions.

[0176] Apparatus: Dynamic viscoelasticity measuring apparatus, manufactured by UBM Co., Ltd. Mode: Tension mode Test piece: Length 32 mm x Width 5 mm Temperature range: -60°C to 60°C Heating rate: 2°C / min Initial strain: 10% Dynamic strain: 0.025% Chuck distance: 20 mm Measurement frequency: 10 Hz

[0177] The wet grip performance was evaluated by determining the value of tan δ at 0° C. Samples with a high tan δ have excellent wet grip performance.

[0178] (2) Low Viscosity (ML Measurement) The Mooney viscosity (ML: dN m) of 6 g of the unvulcanized rubber composition was measured using a rotorless rheometer (manufactured by Toyo Seiki Seisakusho, Ltd.) at a temperature of 160°C.

[0179] (3) Vulcanization stability (T5) Vulcanization stability was evaluated in accordance with JIS K6300-1 (2013).

[0180] More specifically, the Mooney viscosity of 30 g of the unvulcanized rubber composition was measured using a Mooney Viscometer (AM-4, manufactured by Toyo Seiki Seisakusho, Ltd.). The measurement temperature was 125°C, the preheating time was 1 minute, and the rotor used was an L-type rotor. From the measurement results, a Mooney viscosity-time curve was obtained.

[0181] Next, based on the Mooney viscosity-time curve, the time (T5 (min)) until the Mooney viscosity increased by 5 points from the minimum Mooney viscosity (Vm) was measured. Then, the vulcanization stability was evaluated based on T5. Note that a higher T5 value indicates better vulcanization stability.

[0182] (4) Rubber strength (M300) The mechanical strength of the vulcanized rubber (hereinafter referred to as rubber strength) was evaluated in accordance with JIS K6251 (2017).

[0183] More specifically, the tensile strength of the vulcanized rubber was measured using an autograph (AG-20kNI, manufactured by Shimadzu Corporation). The shape of the measurement sample was a dumbbell No. 3, and the tensile speed was 500 mm / min. From the measurement results, an SS curve (stress-strain curve) was obtained.

[0184] Next, based on the SS curve, the tensile stress at 300% elongation (M300 (N / mm ２ ) was measured. Rubber strength was evaluated based on M300. Note that a higher M300 value indicates better rubber strength.

[0185]

[0186]

[0187]

[0188]

[0189]

[0190]

[0191]

[0192] The above invention is provided as an exemplary embodiment of the present invention, but it is merely an example and should not be interpreted as being limiting. Modifications of the present invention that are obvious to those skilled in the art are intended to be included in the scope of the following claims.

[0193] The rubber additive, rubber composition and tire of the present invention are suitably used, for example, in the fields of vehicle tires and aircraft tires.

Claims

1. A rubber additive containing an ester compound, the ester compound containing a rosin-based ester compound having three or more ester bonds in one molecule, and a fatty acid-based ester compound having three or more ester bonds in one molecule.

2. The rubber additive according to claim 1, wherein the rosin-based ester compound contains a reaction product of a carboxy group-containing component and an alcohol component, the carboxy group-containing component contains a rosin, and the alcohol component contains an alcohol having a valence of three or more.

3. The rubber additive according to claim 2, wherein the content of abietadienoic acid is 50 mass% or less based on the total amount of the rosins.

4. The rubber additive according to claim 1, wherein the fatty acid ester compound contains a reaction product of a carboxy group-containing component and an alcohol component and / or contains an oil or fat, the carboxy group-containing component contains a fatty acid, and the alcohol component contains an alcohol having a valence of three or more.

5. The rubber additive according to claim 4, wherein the fatty acids have an iodine value of 170 or less, and / or the fatty acids used as raw materials for the oils and fats have an iodine value of 170 or less.

6. The rubber additive according to claim 1, wherein the ester compound contains a reaction product of a carboxy group-containing component and an alcohol component, the carboxy group-containing component contains rosins and fatty acids, and the alcohol component contains a trihydric or higher alcohol.

7. The rubber additive according to claim 6, wherein said ester compound comprises a collective reaction product of said rosins and said fatty acids with said alcohol component.

8. The rubber additive according to claim 6, wherein the ester compound contains a mixture of a reaction product of the rosins and the alcohol component, and a reaction product of the fatty acids and the alcohol component.

9. The rubber additive according to claim 6, wherein the fatty acid has an iodine value of 170 or less.

10. The rubber additive according to claim 6, wherein the content of abietadienoic acid is 50 mass% or less based on the total amount of the rosins.

11. A rubber composition comprising the rubber additive according to any one of claims 1 to 10.

12. A tire comprising a molded product of the rubber composition according to claim 11.

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