JP2020128464A - Resol type alkylphenol-formaldehyde co-condensation resin and rubber composition containing the resin - Google Patents

Abstract

To provide a resin that, when used as a resin crosslinker, can improve a crosslink rate compared with the conventionally well-known resol type alkylphenol-formaldehyde co-condensation resin, and does not cause reduction in the crosslink density of resultant rubber.SOLUTION: The problem is solved by a resol type alkylphenol-formaldehyde co-condensation resin obtained by mixing a high molecular resin and a low molecular resin, the co-condensation resin having methylene groups and dimethylene ether groups at fixed rates.SELECTED DRAWING: None

Description

The present invention relates to a resole-type co-condensation resin containing constituent units derived from p-tert-octylphenol and formaldehyde, a method for producing the resin, and a rubber composition containing the resin.

As a method for producing a crosslinked rubber having excellent heat resistance, a method using a resol type alkylphenol/formaldehyde cocondensation resin as a crosslinking agent is generally performed. However, the resol-type alkylphenol/formaldehyde co-condensation resin generally used in this method is not yet satisfactory in the cross-linking property, and improvement in the cross-linking property is required. As one of the methods for improving the cross-linking property, a method of increasing the molecular weight of the resol-type alkylphenol-formaldehyde co-condensation resin can be considered, but in general, when the molecular weight of the resin increases, the softening point also rises, so as a cross-linking agent, It is known that when used, the dispersibility in rubber deteriorates and a uniform rubber composition cannot be obtained.

As a method of solving such a problem, for example, the co-condensed resin is mixed with a certain amount of an additive capable of reducing the softening point (oil such as naphthenic oil, plasticizer, etc., hereinafter referred to as softening agent). A method is known in which the resin composition prepared as described above is used as a crosslinking agent (for example, Patent Documents 1 and 2).

JP, 2006-8923, A JP, 2006-63320, A

Based on the description of the above-mentioned document, the present inventors tried to reduce the softening point by mixing a softening agent with a co-condensed resin having a high molecular weight, and no decrease in the predetermined softening point was observed. In order to eliminate the above, it is confirmed that a softening agent in an amount exceeding the amount specified in the above literature is necessary, while the use of the required amount of the softening agent reduces the crosslinking rate and results in a crosslinked rubber obtained. It was found that the crosslink density also decreased.

An object of the present invention is to improve the crosslinking rate as compared with conventionally known resol type alkylphenol-formaldehyde co-condensation resins when used as a crosslinking agent, and to prevent the crosslinking density of the obtained crosslinked rubber from decreasing. It is to provide an alkylphenol-formaldehyde co-condensation resin.

As a result of intensive studies conducted by the present inventors to solve the above-mentioned problems, a resole-type cocondensation resin containing a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde, wherein dimethylene in the cocondensed resin is contained. It has been found that the above problems can be solved by setting the ratio of the ether group and the methylene group within a certain range. Specifically, the following inventions are included.

[1]
A resol-type co-condensation resin containing a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde, wherein the dimethylene ether group is from 0.30 to 0 per mol of the structural unit derived from p-tert-octylphenol. A co-condensation resin having 0.40 mol and a methylene group of 0.45 to 0.55 mol.

[2]
The co-condensation resin according to [1], which has a number average molecular weight of 1,700 to 2,300.

[3]
A resol type co-condensation resin having a number average molecular weight of 1,500 to 2,300 and/or a resin liquid containing the resin, which contains a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde, and p-tert. -A resol type co-condensation resin having a number average molecular weight of 500 to 800 and/or a resin liquid containing the resin, which contains a structural unit derived from octylphenol and a structural unit derived from formaldehyde, is mixed at 100°C to 130°C. 1] or the method for producing the co-condensed resin according to [2].

[4]
A resole-type co-condensation resin having a number average molecular weight of 500 to 800, which contains a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde, has a formaldehyde content of 2.5 to 3 with respect to 1 mol of p-tert-octylphenol. The method for producing a co-condensation resin according to [3], which is a resol-type co-condensation resin obtained by reacting 0.5 mol.

[5]
The amount of the resole-type co-condensation resin having a number average molecular weight of 500 to 800, which contains a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde, is derived from a structural unit derived from p-tert-octylphenol and formaldehyde. Of the cocondensation resin according to [3] or [4], which is 5 to 40 parts by weight with respect to 100 parts by weight of the resol-type cocondensation resin having a structural unit and a number average molecular weight of 1,500 to 2,300. Production method.

[6]
A rubber composition containing the co-condensation resin according to [1] or [2] and a rubber.

[7]
A crosslinked rubber obtained by crosslinking the rubber composition according to [6].

According to the present invention, when used as a cross-linking agent, the cross-linking speed is improved and the cross-linking density of the cross-linked rubber is not reduced as compared with conventionally known re-sol-type alkylphenol-formaldehyde co-condensation resins. It becomes possible to provide an alkylphenol-formaldehyde co-condensation resin.

<Resol type co-condensation resin>
The resole-type co-condensation resin of the present invention essentially requires a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde, and is contained in an amount of 0.30 to 0.0.0 per 1 mol of the structural unit derived from p-tert-octylphenol. It contains 40 mol of dimethylene ether groups and 0.45 to 0.55 mol of methylene groups in the main chain. From the viewpoint of improving the performance of the crosslinked rubber, it is preferable that 0.50 to 0.55 mol of a methylene group is contained with respect to 1 mol of the structural unit derived from p-tert-octylphenol.

The resol type co-condensation resin of the present invention may contain a constituent unit derived from a phenol other than p-tert-octylphenol. Examples of such phenols include phenols having, as a substituent, an optionally branched alkyl group having 1 to 12 carbon atoms or a phenyl group. Specifically, for example, pn-octylphenol, p-tert-amylphenol, p-tert-butylphenol, p as a phenol having a C1-12 alkyl group which may have a branch as a substituent Examples of phenols having a phenyl group as a substituent such as -cresol and p-nonylphenol include p-phenylphenol and the like. Among these phenols, phenols having an optionally branched alkyl group having 1 to 8 carbon atoms or a phenyl group are preferable, and p-tert-amylphenol or p-tert-butylphenol is more preferable.

When it contains a structural unit derived from phenols other than p-tert-octylphenol, the structural unit derived from p-tert-octylphenol is 80 mol% with respect to the structural units derived from all phenols in the resole-type co-condensed resin of the present invention. The above is preferable.

The number average molecular weight of the resole type co-condensation resin of the present invention is usually 1,700 to 2,300, preferably 2,000 to 2,300.

The resol type co-condensation resin of the present invention has a softening point of usually 120° C. or lower, preferably 80 to 110° C. By setting the softening point to 120° C. or less, the dispersibility in preparing the rubber composition is improved, so that the temperature at the time of kneading the rubber can be lowered and the rubber composition of the present invention can be prepared more easily. Becomes

<Method for producing resol type co-condensed resin>
The resole-type co-condensation resin of the present invention includes a constitutional unit derived from p-tert-octylphenol and a constitutional unit derived from formaldehyde, and has a number average molecular weight of 1,500 to 2,300. Molecular resin) and/or a resin liquid containing the resin, and a resol type co-condensation containing a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde and having a number average molecular weight of 500 to 800. It can be produced by mixing a resin (hereinafter sometimes referred to as a low molecular weight resin) and/or a resin liquid containing the resin at 100°C to 130°C.

The above-mentioned polymer resin may be produced by a known method (for example, the method described in Examples of JP-A-02-284910), or a commercially available product (for example, Takki Roll 201 manufactured by Taoka Chemical Co., Ltd.) may be used. .. The resin liquid containing the polymer resin may be prepared by dissolving the polymer resin in an organic solvent described later, or obtained by producing the polymer resin in the presence of the organic solvent described below. Good.

Examples of the organic solvent that may be contained in the resin liquid include aliphatic hydrocarbons and aromatic hydrocarbons. Specific examples thereof include heptane and octane as the aliphatic hydrocarbon, and toluene, xylene, mesitylene and the like as the aromatic hydrocarbon. Among these organic solvents, aromatic hydrocarbons are preferable, and toluene and xylene are more preferable. One of these organic solvents may be contained, or two or more of them may be contained if necessary.

The above low molecular weight resin can be produced, for example, by reacting p-tert-octylphenol with formaldehyde in the presence of an organic solvent and a base (hereinafter, this reaction may be referred to as a condensation reaction).

The condensation reaction may be carried out by using phenols other than p-tert-octylphenol in combination with p-tert-octylphenol. In that case, examples of the phenols other than p-tert-octylphenol that can be used include phenols having an optionally branched alkyl group having 1 to 12 carbon atoms or a phenyl group as a substituent. .. Specifically, for example, pn-octylphenol, p-tert-amylphenol, p-tert-butylphenol, p as a phenol having a C1-12 alkyl group which may have a branch as a substituent. Examples of phenols having a phenyl group as a substituent, such as -cresol and p-nonylphenol, include p-phenylphenol. Among these phenols, phenols having an optionally branched alkyl group having 1 to 8 carbon atoms or a phenyl group are preferable, and p-tert-amylphenol or p-tert-butylphenol is more preferable.

As the formaldehyde used in the condensation reaction, for example, a formaldehyde solution or a compound that can easily generate formaldehyde can be used. Specifically, for example, an aqueous formaldehyde solution (formalin) or an alcohol solution is used as the formaldehyde solution, and paraformaldehyde or trioxane is an example of a compound capable of easily generating formaldehyde. The amount of formaldehyde used is usually 1 to 4 mol, preferably 2.5 to 3.5 mol, based on 1 mol of the total amount of all phenols used in the condensation reaction. When the amount of formaldehyde used is 1 to 4 mol, the number average molecular weight of the resol type co-condensation resin can be set to 500 to 800 by the method described later.

Examples of the base used in the condensation reaction include alkali metal hydroxides and alkali metal carbonates. Specifically, examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide, and lithium hydroxide, and examples of the alkali metal carbonate include sodium carbonate and potassium carbonate. These bases may be used as they are or as a solution (for example, an aqueous solution, an alcohol solution, etc.), but an aqueous solution is preferable from the viewpoint of reactivity and easy handling. For example, when an alkali metal hydroxide is used as an aqueous solution, its concentration is usually 20 to 50% by weight. The amount of the base used is usually 0.25 to 0.35 equivalent (mol) with respect to 1 equivalent (mol) of the total amount of all phenols used in the condensation reaction.

Examples of the organic solvent used in the condensation reaction include aliphatic hydrocarbons and aromatic hydrocarbons. Specific examples thereof include heptane and octane as the aliphatic hydrocarbon, and toluene, xylene, mesitylene and the like as the aromatic hydrocarbon. Among these organic solvents, aromatic hydrocarbons are preferable, and toluene and xylene are more preferable. These organic solvents may be used alone or in combination of two or more if necessary.

The condensation reaction is carried out, for example, by placing each of the above-mentioned compounds in a reaction vessel and usually at 40 to 100° C., preferably 60 to 90° C., and the number average molecular weight of the resol type co-condensation resin in the reaction liquid is in the range of 500 to 800. Do up to. The number average molecular weight in the reaction solution is determined by sampling a part of the reaction solution and using the method described in the section of Examples below (a method for measuring the number average molecular weight using gel permeation chromatograph (GPC)). Can be measured. By setting the reaction temperature to 40° C. or higher, a sufficient reaction rate can be obtained, and by setting the reaction temperature to 100° C. or lower, the reaction rate can be suppressed and gelation (polymerization) can be avoided. It will be easy.

After the condensation reaction, the obtained reaction solution may be used as it is as a resin solution in a mixing step described later, but usually, the reaction solution is once neutralized with an acid (hereinafter, this step may be referred to as a neutralization step There is) used. Before carrying out the neutralization step, an organic solvent may be added to the reaction solution obtained by the condensation reaction to dilute the reaction solution. As the organic solvent used for dilution, the same organic solvent as that which can be used in the condensation reaction can be used.

Examples of acids that can be used in the neutralization step include inorganic acids and organic acids. Specifically, examples of the inorganic acid include sulfuric acid, hydrochloric acid, phosphoric acid and the like, and examples of the organic acid include acetic acid, oxalic acid, formic acid and the like. These acids may be used alone or in combination of two or more as required. An aqueous solution of these acids may be used, and when the aqueous solution is used, the concentration thereof is usually 5 to 50% by weight. The amount of the acid used is usually 0.3 to 2 equivalents (mol), preferably 0.5 to 1.5 equivalents (mol) with respect to 1 equivalent (mol) of the base used in the condensation reaction.

The neutralization step is carried out by mixing the reaction liquid obtained in the condensation step and the acid at 40 to 80°C, preferably 60 to 80°C. After mixing, water may be added if necessary, and the aqueous layer may be removed after stationary separation (hereinafter referred to as a water washing operation). Further, if necessary, the inorganic component in the organic layer may be removed by repeating the water washing operation a plurality of times.

After the above-mentioned neutralization step, the obtained reaction solution may be used as a resin solution as it is in the mixing step described later, or a part or all of the resin solution may be concentrated.

Subsequently, a step of mixing the polymer resin and/or the resin solution containing the resin with the resin solution containing the low molecular weight resin and/or the resin at 100°C to 130°C (hereinafter, may be referred to as a mixing step. ) Will be described in detail.

In the mixing step, the polymer resin and/or the resin liquid containing the resin and the resin liquid containing the low molecular weight resin and/or the resin are placed in a reaction vessel, mixed at 100 to 130° C., and then mixed if necessary. The resol type co-condensation resin of the present invention can be obtained by concentrating and removing a part or all of the solvent contained in the solution. By carrying out the mixing step within the above temperature range, it becomes possible to obtain the resol type co-condensation resin of the present invention having the above-mentioned characteristics and to suppress the increase of the softening point of the obtained co-condensation resin. Further, the concentration may be performed at the same time as the above mixing operation.

In the mixing step, the amount of the low molecular weight resin used is usually 1 to 50 parts by weight, preferably 5 to 40 parts by weight, based on 100 parts by weight of the polymer resin.

<Rubber composition>
Next, the rubber composition containing the resol type co-condensation resin of the present invention and a rubber will be described in detail.
The rubber composition of the present invention contains the above-mentioned resol type co-condensation resin and rubber, and can be typically obtained by kneading the resol type co-condensation resin and rubber.

The rubber contained in the rubber composition of the present invention may be any rubber as long as it has a double bond and can be crosslinked with a resin. Specific examples thereof include natural rubber (NR) and styrene-butadiene rubber (SBR). , Isoprene rubber (IR), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR) and the like. Of these, butyl rubber (IIR) is preferable.

In the rubber composition of the present invention, in addition to the above-mentioned rubber, the resole-type co-condensed resin of the present invention, various kinds such as an antioxidant, a filler such as carbon black or the like, which is usually blended with the rubber, a calcined clay, etc., if necessary. It may contain an inorganic filler, zinc white, stearic acid, oils and the like.

The crosslinked rubber of the present invention is obtained by crosslinking the rubber composition of the present invention described above. As a method for crosslinking the rubber composition of the present invention, for example, a method in which the process from molding to completion of crosslinking is carried out by a pressure press or the like, and molding and primary crosslinking are carried out by a pressure press, for example, for 5 minutes to 15 minutes. Then, a method of carrying out secondary crosslinking in an oven or an electric furnace, for example, for 30 minutes to 4 hours can be mentioned. From the viewpoint of the productivity of the crosslinked rubber, a method of performing the primary crosslinking and the secondary crosslinking separately. Is preferred.

The cross-linking temperature of the rubber composition of the present invention is not different from that when the conventional resin cross-linking agent is used, and specifically, for example, 130 to 230°C, preferably 160 to 210°C, more preferably 180 to 200°C. Is.

The crosslinked rubber of the present invention can be used as various rubber products, and particularly preferably used as packings, O-rings, bladders and the like.

Hereinafter, the present invention will be described more specifically by showing Examples, Comparative Examples, and Reference Examples (hereinafter sometimes referred to as Examples and the like).

[1] Gel permeation chromatograph (GPC) analysis condition used device: HLC-8220GPC (manufactured by Tosoh Corporation)
Detector: RI (differential refraction) detector column: TSK guard column SUPER HZ-L (manufactured by Tosoh Corporation)
+TSK-GEL SUPER HZ1000 (4.6mmφ×150mm)
+TSK-GEL SUPER HZ2500 (4.6mmφ×150mm)
+TSK-GEL SUPER HZ4000 (4.6mmφ×150mm)
Column temperature: 40°C
Injection volume: 10 μL
Carrier and flow rate: tetrahydrofuran 0.35 mL/min
Standard substance for obtaining reduced molecular weight (preparation of calibration curve): 1,1-bis(4-hydroxyphenyl)cyclohexane (FW268) and phenol (FW94) were added to TSK-GEL standard polystyrene kit (PS-oligomer kit). , A calibration curve was created.
Sample preparation: About 0.02 g of the sample to be measured was dissolved in 10 mL of tetrahydrofuran.

Based on the results obtained by the above GPC analysis, the number average molecular weight (Mn) of the resol type co-condensation resin was calculated as follows.
Method for calculating the number average molecular weight (Mn) of the resol-type cocondensation resin: The multimodal peaks obtained by GPC analysis were treated as a group, and the number average molecular weight (Mn) of the resol-type cocondensation resin was calculated. When calculating the average molecular weight of the resol-type co-condensed resin, the peak corresponding to the organic solvent in the resin liquid was excluded.

[2] Measurement of unreacted monomer The unreacted monomer was quantified by gas chromatography under the following conditions.
Equipment used: Shimadzu Corporation Gas Chromatograph GC-2014
Column: Glass column outer diameter 5 mm x inner diameter 3.2 mm x length 3.1 m
Filler: Filler Silicone OV-17 10% Chromosorb WHP 80/100 mesh, max. temp. 340°C
Column temperature: 80℃→280℃
Vaporization chamber temperature: 250°C
Detector temperature: 280℃
Detector: FID
Carrier: N ₂ (40 ml/min)
Combustion gas: Hydrogen (60 kPa), air (60 kPa)
Injection volume: 2 μL
Sample preparation conditions: 1 g of the resol type co-condensation resin was dissolved in 10 mL of a standard solution (acetone solution of anisole (1 g/200 mL)) and analyzed under the above conditions.
Quantitative method: Internal standard method (GC-IS method).

[3] Measurement of softening point It was measured by a method according to JIS-K2207. As the bath liquid, glycerin (special grade manufactured by Kishida Chemical Co., Ltd.) was used.

[4] Ratio of Constituent Units of Co-Condensed Resin or Resin Composition ¹ H-NMR analysis was performed by a method based on the following conditions.
Device: JEOL's "JMN-ECS" (400MHz)
Solvent: Deuterated chloroform 0.03% (v/v) TMS
Sample: Approximately 5 mg was subjected to dissolution analysis with 0.75 mL of solvent Sample: Resol type co-condensation resin was crushed and subjected to ¹ H-NMR analysis.

Chemical shift of each component for attribution of ¹ H-NMR analysis results: Tetramethylsilane was used as a reference (0 ppm), and the peaks shown below were used as the peaks of the respective components.
Proton derived from p-tert-octyl group: 0.5 to 0.8 ppm
Proton of methylene group derived from formaldehyde: 3.5 to 4.1 ppm
Proton of dimethylene ether group derived from formaldehyde: 4.2 to 4.8 ppm

<Production Example 1: Synthesis example of resin liquid containing polymer resin (resin liquid-1)>
In a four-necked flask equipped with a reflux condenser and a thermometer, 618.0 g (3.00 mol) of p-tert-octylphenol, 195.8 g (6.00 mol) of 92% paraformaldehyde, and 48% aqueous sodium hydroxide solution were added. 75.0 g (0.90 mol) and 185 g of toluene were added, the internal temperature was raised to 60° C. with stirring, the mixture was stirred at the same temperature for 1 hour, further raised to 90° C., and then stirred at the same temperature for 4 hours. ..
Then, the reaction liquid was cooled to 70° C., 171.0 g of water, 370 g of toluene and 147.1 g of 30% sulfuric acid were added thereto, and the mixture was stirred at 70° C. for 30 minutes and allowed to stand, and then the aqueous layer was separated. Then, 171.0 g of water was added to the toluene layer, and the mixture was stirred at 70° C. for 30 minutes and allowed to stand, and then the aqueous layer was separated. By repeating the same operation twice, 1286.5 g of a resin liquid (resin liquid-1) containing a polymer resin was obtained.

The number average molecular weight (Mn) of the resol type co-condensed resin contained in the obtained resin liquid was as follows.
-Number average molecular weight (Mn): 1,569

<Production Example 2: Synthesis example of resin liquid (resin liquid-2) containing low molecular weight resin>
In a four-necked flask equipped with a reflux condenser and a thermometer, 420.0 g (2.04 mol) of p-tert-octylphenol, 496.7 g (6.12 mol) of 37% formaldehyde and 48% aqueous sodium hydroxide solution 17 were added. 0.0g (0.20 mol) was added, the internal temperature was raised to 60°C with stirring, the mixture was stirred at the same temperature for 1 hour, further raised to 90°C, and then stirred at the same temperature for 4 hours.
Thereafter, the reaction solution was cooled to 70° C., 67.0 g of water, 300 g of toluene and 32.7 g of 30% sulfuric acid were added thereto, and the mixture was stirred at 70° C. for 30 minutes and allowed to stand, and then the aqueous layer was separated. Then, 67.0 g of water was added to the toluene layer, the mixture was stirred at 70° C. for 30 hours, and allowed to stand, and then the aqueous layer was separated. Further, by repeating the same operation twice, 837.5 g of a resin liquid (resin liquid-2) containing a low molecular weight resin was obtained.

The number average molecular weight (Mn) of the resol type co-condensed resin contained in the obtained resin liquid was as follows.
-Number average molecular weight (Mn): 668

<Example 1>
To a four-necked flask equipped with a reflux condenser and a thermometer, 90 parts by weight of Resin Solution-1 and 10 parts by weight of Resin Solution-2 obtained by the above method were put, and the internal temperature was 110° C. under normal pressure while stirring. The resol type co-condensation resin (resin-1) of the present invention was obtained by performing concentration for 1 hour until the temperature reached 100° C. and then for 1 hour under reduced pressure of 300 torr and an internal temperature of 120° C.

The physical properties of Resin-1 thus obtained were as follows.
-Number average molecular weight (Mn): 2,077
・Softening point: 98°C
-P-tert-octylphenol: 2.4%
-Ratio of each structural unit to 1 mol of structural unit derived from p-tert-octylphenol of co-condensed resin: dimethylene ether group: 0.32 mol, methylene group: 0.54 mol

<Example 2>
Into a four-necked flask equipped with a reflux condenser and a thermometer, 180 parts by weight of Resin Solution-1 and 20 parts by weight of Resin Solution-2 obtained by the above method were put, and the internal temperature was 110° C. under normal pressure while stirring. The resol type co-condensation resin (resin-2) of the present invention was obtained by performing concentration for 1 hour until the temperature reached 100° C. and then for 1 hour under reduced pressure of 300 torr and an internal temperature of 120° C.

The physical properties of the obtained resin-2 were as follows.
-Number average molecular weight (Mn): 1,701
・Softening point: 95°C
-P-tert-octylphenol: 5.5%
Ratio of each structural unit to 1 mol of structural unit derived from p-tert-octylphenol of co-condensation resin dimethylene ether group: 0.35 mol, methylene group: 0.50 mol

<Comparative Example 1>
Into a four-necked flask equipped with a reflux condenser and a thermometer, 100 parts by weight of the resin liquid-2 obtained by the above method was put, and the pressure was reduced to 160 torr while stirring and the internal temperature reached to 120°C for 1.3 hours. By performing concentration under reduced pressure, a resol type p-tert-octylphenol/formaldehyde cocondensation resin (resin-3) was obtained.

The physical properties of the obtained resin-3 were as follows.
-Number average molecular weight (Mn): 1,031
・Softening point: 79°C
-P-tert-octylphenol: 1.1%
Ratio of each structural unit to 1 mol of structural unit derived from p-tert-octylphenol of co-condensation resin dimethylene ether group: 0.28 mol, methylene group: 0.44 mol

Example 3 Production Example of Rubber Composition of the Present Invention and Crosslinked Rubber Made by Crosslinking the Rubber Composition>
Butyl rubber (Polycerbutyl 402) 100 parts by weight, carbon black (Tokai Carbon Co., Ltd., "SEAST S" (SRF grade)) 50 parts by weight, zinc flower (Shodo Chemical Co., Ltd. zinc flower 2 types) 5 parts by weight, A masterbatch rubber (256 g) containing 100 parts by weight of calcined clay (“BURGESS KE” manufactured by Burgess Pigment Co.) and 1 part by weight of stearic acid (“beads stearic acid camellia” manufactured by NOF CORPORATION) was kept at 20° C. It was put in a 6-inch open roll manufactured by Kansai Roll Co., Ltd. and wound around the roll with a roll width of 2 mm. Then, 15 parts by weight of Resin-1 produced in Example 1 was added, and the material was cut three times. Next, the roll width was set to 0.25 mm, and triangular threading was performed 10 times to knead and prepare 272 g of a rubber composition.
Next, the rubber composition was heated at 190° C. and 6 MPa under pressure for 10 minutes to perform press molding. Then, the press-molded rubber sheet is placed in a vacuum oven heated to 190° C. and heated at 190° C. for 150 minutes under a reduced pressure of 40 mmHg to obtain a crosslinked rubber (crosslinked rubber sheet) obtained by crosslinking the rubber composition. Created.
The following tests and evaluations were performed on the rubber composition and the crosslinked rubber obtained by the above method. The results are shown in Table 1.

<Example 4, Reference Example 1, Comparative Example 2>
A rubber composition and a crosslinked rubber were prepared in the same manner as in Example 3 except that the resin was changed to those shown in Table 1 below, and the following tests and evaluations were performed. The results are shown in Table 1. In addition, Reference Example 1 is a commercially available resin cross-linking agent, which is a resol type co-condensation resin (Takki Roll 201 manufactured by Taoka Chemical Industry Co., Ltd.) containing a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde. It was used as a resin (in Table 1, the resin crosslinking agent is referred to as resin 201).

<Rubber composition and cross-linked rubber test method>
(1) Test method A test was carried out by a method according to JIS K6300-2:2001. Specifically, the torque change was measured while heating the rubber composition at 190° C. for 60 minutes using a rotorless rheometer (vibration angle ±3.00°), and each example was used. The time to reach 10% of the maximum torque value obtained in (t10), the time to reach 90% (t90), and the maximum torque (MH (dN·m)) of the rubber composition were measured. In addition, in Table 1, each measured value obtained by the above method is shown as a relative value when each measured value obtained in Reference Example 1 is set to 100.

(2) Evaluation of cross-linking speed and cross-link density Based on the relative values shown in Table 1, the cross-linking speed and cross-link density were evaluated according to the following evaluation methods.
(2-1) Evaluation of cross-linking speed When t10, which indicates the initial cross-linking speed, is 10 points or more higher than in Reference Example 1, the initial cross-linking speed is slow, and when it is 30 points or less, scorch (early cross-linking) may occur. Therefore, those having t10 of 10 points or more and those of 30 points or less with respect to Reference Example 1 were inferior to Reference Example 1. Further, since the smaller the value of t90, which is a guideline for the end point of crosslinking, is, the faster the crosslinking is, so that the value of 5 points or more smaller than that of Reference Example 1 is improved from that of Reference Example 1, and conversely it is large. Since the rate of the end point of crosslinking is slower, the sample having 10 points or more larger than that of Reference Example 1 was judged to be inferior to Reference Example 1. Then, among these two evaluation values, ⊚ indicates that the result is better than each reference example, × indicates that the result is inferior, and ◯ indicates the other one (equivalent to each reference example).

(2-2) Evaluation of Crosslink Density The maximum torque (MH) in the rheometer test was compared with Reference Example 1 respectively, and an increase of 3 points or more relative to Reference Example 1 was considered to be improved from Reference Example 1, and 3 points or more. The decrease is inferior to Reference Example 1, the difference is within ±2 points is equivalent to Reference Example, the improvement is higher than Reference Example, ⊚, the one including inferior result is ×, and Reference Example is equivalent. Was ◯.

Claims (7)

A resol-type co-condensation resin containing a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde, wherein the dimethylene ether group is from 0.30 to 0 per mol of the structural unit derived from p-tert-octylphenol. A co-condensation resin having 0.40 mol and a methylene group of 0.45 to 0.55 mol. The co-condensation resin according to claim 1, having a number average molecular weight of 1,700 to 2,300. A resol type co-condensation resin having a number average molecular weight of 1,500 to 2,300 including a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde, and/or a resin liquid containing the resin, and p-tert- The resol type co-condensation resin having a number average molecular weight of 500 to 800 containing a structural unit derived from octylphenol and a structural unit derived from formaldehyde and/or a resin liquid containing the resin is mixed at 100°C to 130°C. Or the method for producing the co-condensed resin according to item 2. A resol type co-condensation resin having a number average molecular weight of 500 to 800 including a structural unit derived from p-tert-octylphenol and a structural unit derived from formaldehyde is 2.5 to 3% formaldehyde per mol of p-tert-octylphenol. The method for producing a co-condensation resin according to claim 3, which is a resol-type co-condensation resin obtained by reacting 5 mols. The amount of the resole-type co-condensation resin having a number-average molecular weight of 500 to 800 including the constituent unit derived from p-tert-octylphenol and the constituent unit derived from formaldehyde is the constituent unit derived from p-tert-octylphenol and the constituent derived from formaldehyde. The method for producing a cocondensation resin according to claim 3 or 4, wherein the number average molecular weight of the unit is 5 to 40 parts by weight with respect to 100 parts by weight of the resol-type cocondensation resin having a number of 1,500 to 2,300. A rubber composition containing the co-condensation resin according to claim 1 or 2 and a rubber. A crosslinked rubber obtained by crosslinking the rubber composition according to claim 6.