JPS62115046A - Rubber composition - Google Patents

Abstract

PURPOSE:To contemplate improvements in modulus, hardness and elongation after vulcanization, by providing a rubber compsn. by blending solid rubber with a specified novolak type addition condensation resin. CONSTITUTION:This rubber compsn. contains 100pts.wt. solid rubber (A) and 1-50pts.wt. cyclo-pentenyl phenol compd. of the formula (wherein R1, R2 are each H, an alkyl, halogen or cyclopentenyl group; R1, R2 may be the same or different groups; hydrogen atoms are attached at least two positions among p- and o- positions against OH group) or material which has a weight-average MW of 4,000-14,000 and is a novolak type addition condensation resin derived from said compd., cresol or an aldehyde (B). Examples of the starting aldehyde for said resin are formaldehyde, paraformaldehyde and accetaldehyde.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application j) The present invention relates to a rubber composition having excellent hardness, elastic modulus, and elongation.

(Prior Art) Conventionally, in order to increase the hardness and elastic modulus of a rubber composition after vulcanization, large amounts of compounding agents such as carbon blank and sulfur have been blended into rubber. It is certainly possible to increase the hardness and elastic modulus of a rubber composition after vulcanization by blending a large amount of carbon black into rubber, but this results in a significant decrease in elongation and poor wettability of the rubber during the processing process. The electric power load on the Banbury mixer increased and the winding condition on the roll was extremely poor, making it difficult to put it into practical use. on the other hand.

It has been attempted to increase the hardness and elastic modulus of rubber by adding a large amount of sulfur, but the elongation of this rubber composition after vulcanization is significantly reduced, and the high sulfur content also causes sulfur to reach the rubber surface during extrusion. The plumping phenomenon of precipitation and crystallization is severe, making molding workability difficult and reducing the yield of the product, which is undesirable.

Therefore, in recent years, in order to improve the hardness and elastic modulus of rubber, thermosetting resins such as novolak-type phenolic resins and novolak-type modified phenolic resins have been added while keeping the amount of carbon black and sulfur to a practical level. There are an increasing number of cases where this is the case.

(Problems to be Solved by the Invention) However, when a thermosetting resin is blended, the hardness and elastic modulus can be improved to some extent while suppressing a decrease in the elongation of the rubber. However, the ones that can fully satisfy the hardness 9 elastic modulus and elongation required for recent rubbers are:
The current situation is that it has not been discovered.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rubber composition that has a high modulus of elasticity after vulcanization, exhibits excellent elongation, and particularly has excellent hardness.

(Means for Solving the Problems) The present invention solves the above problems by using a specific novolak type addition condensation resin having a specific weight average molecular weight as a rubber compounding agent.

That is, 9 the present invention comprises (A) 100 parts by weight of solid rubber and tB) general formula [1] (in formula 1, R1 and R2 are hydrogen, an alkyl group,
Indicates a halogen or cyclopentenyl group, which may be the same or different, in the above formula.

The present invention relates to a rubber composition comprising a novolac type addition condensation resin of at least one of p-position and ○-position with respect to an OH group and an aldehyde and having a weight average molecular weight of 4.000 to 14.000.

Examples of the solid rubber of the present invention include natural rubber, polyisoprene rubber, polybutadiene rubber, and styrene-butadiene copolymer rubber.

The novolac type addition condensation resin of the present invention has the above general formula (1
It can be obtained by reacting a cyclopentenylphenol compound represented by the following formula, cresol, and an aldehyde in the presence of an acidic catalyst.

As the cyclopentenylphenol compound represented by the general formula [I], O-cyclopentenylphenol,
m-Cyclopentenylphenol.

Examples include p-cyclopentenylphenol, 3-methyl-4-cyclopentenylphenol, and 4-dicyclopentenylphenol, and monoalkyl substituents other than those listed here include those shown in Table 1.

Table 1 Monoalkyl substituent Table 1 (Continued) In Table 1, the propyl group can be either n-propyl group or isopropyl group, and the butyl group can be n-butyl group,
It is either a 5ec-butyl group or a tert-butyl group, and the pentyl group is either an n-pentyl group or other structurally isomeric groups.

The cresol used in the present invention is O-cresol, m-
Cresol, p-cresol and mixtures thereof may also be used.

Examples of the aldehyde used in the present invention include formaldehyde, paraformaldehyde, and acetaldehyde.

The acidic catalyst used in the present invention is sulfuric acid.

These include mineral acids such as nitric acid, hydrochloric acid, and boric acid, and organic acids such as I)-) luenesulfonic acid, oxalic acid, and formic acid.

A cyclopentenyl group represented by the general formula (1) is preferably used. If it is less than 10/90, the elongation of the rubber composition will not be sufficiently improved by using the cyclopentenylphenol compound.

20/80 to 50150 is preferred.

The amount of aldehyde is the total amount of cyclopentenylphenol compound represented by the above general formula (1) and hycresol.
0.5 to 1.1 moles per mole is preferred. If the amount of aldehyde is too small, the resulting resin will have a small molecular weight.
If the amount is too high, the resin will gel during production.

The acidic catalyst is o, o o s to 0 per total amount of one reactant.
．． It is preferably 3% by weight, and preferably 01 to 0.2% by weight. If the amount of acidic catalyst is too small, the reaction rate will be slow, and if it is too large, side reactions such as alkylation reactions will easily occur, making gelation more likely to occur.

The reaction in the present invention is an addition condensation reaction of the above-mentioned cyclopentenylphenol compound, cresol, and aldehyde, and is preferably carried out at 50 to 130°C. If the reaction temperature is too low, the addition condensation reaction will be slow; if the reaction temperature is too high, an alkylation reaction will occur between the double bond of the cyclopentenyl group and the phenol nucleus of the individual molecules, which may sometimes result in gelation. A suitable reaction time is 1 to 4 hours.

Preferably, the reaction is carried out in an organic solvent. As the solvent, aromatic solvents such as toluene, benzene, and xylene, chlorine-containing solvents such as chloroform, carbon tetrachloride, and chlorobenzene, and ethyl ether can be used.

After the reaction is complete, neutralize the acidic catalyst with a basic compound such as sodium hydroxide, potassium hydroxide, or sodium carbonate.
After removing the neutralized salt by filtration or the like, the solvent and unreacted monomers can be removed by distillation to isolate the novolak type addition condensation resin of the present invention.

The novolak-type addition condensation resin of the present invention has a cyclopentenyl group, and nuclear magnetic resonance spectroscopy shows that the hydrogen bonded to the carbon constituting the double bond in the cyclopentenyl group has a direct correlation of 5.8 pprn. The cyclopentenyl group can be confirmed by observing the absorption based on the cyclopentenyl group, and the cyclopentenyl group can be quantified by comparing the area intensity of this absorption with the area intensity of the absorption based on the hydrogen of the methylene group or substituted methylene group.

The novolak type addition condensation resin of the present invention has a weight average molecular weight of 4.000 to 14,000. If the weight average molecular weight is too low, the hardness of the rubber composition tends to decrease, and if the weight average molecular weight is too high, the dispersibility in rubber decreases, and in particular, the hardness tends to decrease.

In the present invention, the 2 weight average molecular weight is determined by gel permeation chromatography in terms of standard polystyrene.

In the present invention, (A) solid rubber and (B) novolac type addition condensation resin are (B)
It contains 1 to 50 parts by weight, preferably 5 to 20 parts by weight. (A) If Bl is less than 1 part by weight, the elongation of the rubber composition will not be sufficiently improved, and if (B) exceeds 50 parts by weight, the elongation of the rubber composition will tend to decrease rapidly. .

The composition according to the present invention further includes a curing agent for novolak type addition condensation resin such as hexamethylenetetramine, sulfur,
- Inorganic vulcanizing agents such as sulfur chloride; 2 Organic vulcanizing agents such as morpholine disulfide and alkylphenol disulfide;
Modification of vulcanization accelerators such as acetaldehyde-ammonia adducts, formaldehyde-paratoluidine condensation products, diphenylguanidine, 2-mercaptobenzothiazole, N-cyclohexyl-2-benzothiazolylsulfenamide, carbon black, etc. Kneading aids such as additives, process oils, additives such as zinc white, magnesium oxide, stearic acid, etc. can be added as appropriate according to conventional methods.

Among these, the amount of the above-mentioned vulcanizing agent to be used varies depending on the type of the vulcanizing agent, but it is preferably added in an amount of 0.5 to 5% by weight based on the rubber. If the amount of the vulcanizing agent is too small, the hardness of the rubber composition will decrease, and if it is too large, the elongation will tend to decrease. When sulfur is used, it is preferably 1.5 to 5% by weight, based on the rubber.

The vulcanization accelerator is preferably added in an amount of 20 to 250% by weight based on the vulcanizing agent.

The above curing agent is 0 to 0 to novolac type addition condensation resin.
Preferably, 20% by weight is used. If there is too much curing agent, the elongation of the rubber composition tends to decrease. Further, in order to impart preferable hardness and elongation to the rubber composition, it is preferable that the curing agent is added in an amount of 5 to 15% by weight based on the novolak type addition condensation resin. Note that hexamethylenetetramine also functions as a vulcanization accelerator.

(Example) First, a synthesis example of a novolac type addition condensation resin will be shown.

Synthesis Example 1 Installing a fractionating head with a stirrer, thermometer and cooling tube fc
Into 1000 ml four rose paraple flasks, add 240 g of cyclopentenylphenol (1,5 moI! Ortho form/para form ratio = 1/6.8: molar ratio), cresol 162 g (1.5 mol meta form/para form = 3/ 2; molar ratio), and paraformaldehyde 112. ．． 5g (3m
In addition, 1809% of toluene was added as a solvent, and 0.969% of oxalic acid was used as a catalyst. Add 0.069% of hydrochloric acid, start heating and stirring, and heat at 55-65°C for 1 hour at 75-65°C.
1.5 hours at 85°C, then 2 hours under reflux at 95-103°C.
The reaction proceeded for ~3 hours. After the reaction, the reaction solution was returned to room temperature, 150 g of toluene was added, and the solution was neutralized with a 30% NaOH aqueous solution. After removing the neutralized salt by filtration, it is desoluted using a vacuum pump, and the degree of vacuum is 30 to 60 mmHg, 220°C.
Unreacted monomers were removed by distillation under reduced pressure until the softening point reached 120.
A brown novolak-type addition condensation resin was obtained at ℃. Gel permeation chromatography (Hitachi 63)
5A type HLC, R420+R430+R440 column)
The weight average molecular weight was measured in terms of standard polystyrene (the same applies hereinafter) and was found to be 4.520.

Synthesis Example 2 Installing a fractionating head with a stirrer, thermometer and cooling tube &1
In a 000d four-neck, separable flask, 160 g of cyclopentenylphenol (1 mol! Ortho/para ratio = 1/6.5: molar ratio), 216 g of cresol (
Add 2 mol meta body/para body ratio = 3/2: molar ratio) and paraformaldehyde 112.59 (3 moJ),
Furthermore, toluene 1809% as a solvent and oxalic acid 0.969% as a catalyst. After adding 0.069 g of hydrochloric acid and starting heating and stirring, the reaction was carried out under the same conditions as in Synthesis Example 1. The reaction solution was returned to room temperature and 1509 i of toluene was added to give a 30%
Neutralized with NaOH aqueous solution. After removing the neutralized salt by filtration, it is desoluted with a vacuum pump and the degree of vacuum is 30 to 70 mmHg.
, vacuum distillation was carried out to 220°C to remove unreacted monomers to obtain a brown novolac type addition condensation resin with a softening point of 125°C. The weight average molecular weight of this product was 5.700.

Synthesis Example 3 1 with a fractionating head equipped with a stirrer, thermometer and cooling tube
0100O! 160 g of cyclopentenylphenol (1 mo/ortho form/para form ratio = 1/6.5; molar ratio) and 324 g of cresol (
3 moj' meta body/para body ratio = 3/2: molar ratio) and paraformaldehyde 1509 (4 mo/), toluene 2409 as a solvent, and oxalic acid 1 as a catalyst.
．． 289. Hydrochloric acid 0.049 was added, heating and stirring were started, and the reaction was continued at 50 to 60°C for 1 hour, at 78 to 84°C for 1.5 hours, and further under reflux at 95 to 104°C for 2 to 3 hours. . After the reaction 9. Return the reaction solution to room temperature and add 200% of toluene.
g and neutralized with 30% NaOH aqueous solution. Neutralized salts are removed by filtration, and after death, desolubilized with a vacuum pump to reduce pressure to 3.
Vacuum distillation was performed at 0-60 mmHg to 240°C to remove unreacted monomers to obtain a brown novolak type addition condensation resin with a softening point of 140°C. The weight average molecular weight of this product was 7.180.

Synthesis Example 4 The same reaction operation as in Synthesis Example 3 was carried out, and the neutralized salt was removed from the resulting neutralized reaction solution, and after desolvation, the degree of vacuum was 30 to 70 mm.
Hg was distilled under reduced pressure to 250°C to remove unreacted monomers to obtain a brown novolak type addition condensation resin with a softening point of 150°C. The weight average molecular weight of this product is 1λ750
Met.

The results of the above Synthesis Examples 1 to 4 are summarized in Table 2.

1 batch: 1゛ Comparative Synthesis Example 1 1 with a fractionating head equipped with a stirrer, thermometer and cooling tube
000 tri 240 g of cyclopentenylphenol (1,5 mo/ortho form/para form ratio = 1/6.8; molar ratio), cresol 1 in 4 rose paraple flasks
62 g (1.5 mol meta body/para body = 3/2: molar ratio 1 and paraformaldehyde 11L59 (3 moI) was added, and toluene 180B was added as a solvent, para-toluenesulfonic acid 0.699 was added as an M medium, heating,
Start stirring and incubate at 50-60°C for 0.5-1.0 hours, 7
1°θ to 2.0 hours at 8 to 82°C, further 98 to 100
The reaction was allowed to proceed for 1 to 2 hours under reflux at °C. After the reaction, the reaction solution was returned to room temperature, and 150 g of acetone was added to dilute the solution with 30% Na.
Neutralized with OH aqueous solution. After removing neutralizing salts by filtration.

Desolute with a vacuum pump and reduce pressure to 100 mmHg, 20
Distillation was carried out under reduced pressure down to 0°C to remove unreacted monomers to obtain a brown novolak type addition condensation resin with a softening point of 105°C. The weight average molecular weight of this product was 1.890.

Comparative Synthesis Example 2 1 with a fractionator equipped with a stirrer, thermometer and cooling tube
0100O! Cyclopentenylphenol 1609 (1 mot! #ruto/para-isomer ratio = 1/6.5:%ru ratio), cresol 324 g in four rose paraple flasks.
(3 mol! Meta body/para body ratio ≠ 3/2: molar ratio) and 150 g (4 mol) of paraformaldehyde were added,
Furthermore, 240 g of toluene as a solvent and 0.929 g of para-toluenesulfonic acid as a catalyst were added, heating and stirring were started, and the temperature was kept at 50-60°C for 0.5-1 hour, and then at 78-80°C.
The reaction was further continued for 1 to 2 hours under reflux at 95 to 103°C. After the reaction, one reaction solution was returned to room temperature, 200 g of acetone was added, and the solution was neutralized with 304 NaOH aqueous solution. After removing the neutralized salt by filtration, it is desoluted with a vacuum pump, and vacuum distillation is performed at a degree of vacuum of 30 to 60 mmHg to 260°C to remove unreacted monomers, resulting in a brown novolac type addition condensation resin with a softening point of 164°C. I got it. The weight average molecular weight of this product was 20,730.

Comparative Synthesis Example 3 5 with a fractionator equipped with a stirrer, thermometer and cooling tube
Cresol 1089 (1 moJ meta/para body ratio = 3/2; molar ratio), halaformaldehyde 37.59 (1 moJ) in four separable flasks of 00 rnt.
and 709% of toluene as a solvent and 0.329% of oxalic acid as a catalyst. Add 0.029 ml of hydrochloric acid, start heating and stirring, and heat at 70 to 80°C for 0.5 to 1 hour at 90°C.
The reaction was allowed to proceed under reflux for 1 to 3 hours at ~100°C, and then for an additional 1 to 3 hours.
The temperature was raised to 30° C. over about 3 hours, and a reflux dehydration operation was performed. After the reaction 1. Return the reaction solution to room temperature and add 50% acetone.
9 was added and neutralized with 30% NaOH aqueous solution. After removing the neutralized salt by filtration, it is desoluted using a vacuum pump.

Further, vacuum distillation was carried out at a reduced pressure of 100 mmHg to 200°C to remove unreacted monomers, yielding a pale orange novolac phenol resin with a softening point of 130°C. The weight average molecular weight of this product was 4.820.

Next, an example of the present invention will be shown.

Examples 1 to 4 and Comparative Examples 1 to 3 Using the novolak type phenolic resins obtained in Synthesis Examples 1 to 4 and Comparative Synthesis Examples 1 to 3, each component was mixed in the formulation shown in Table 3. This mixture is.

Components other than the sulfur vulcanization accelerator and hexamethylenetetramine were mixed in a B-type Banbury mixer (capacity 250 cc) as usual. Methylenetetramine was kneaded with two rolls at 30-40°C. The obtained rubber composition was press-vulcanized at 150'C, 14 kgf, and 70 m2 for 20 minutes to obtain a vulcanized rubber sheet with a thickness of 2LLIII+.

The hardness of the rubber sheets obtained in Table 3 Kuraguchi Formulation Examples 1 to 4 and Comparative Examples 1 to 3 was measured at room temperature using a JIS A type spring type hardness tester.

The 100% and 300% modulus, tensile strength and elongation were measured by punching out the vulcanized rubber sheet into JIS No. 3 dumbbells and using a Schottspa set tensile strength tester at room temperature. The results are shown in Table 4.

(Effect of the invention) The rubber composition containing the rubber according to the present invention and the novel novolac type addition condensation resin has a high elastic modulus after vulcanization,
It exhibits excellent elongation and particularly has excellent hardness.

Claims (1)

[Claims] 1. (A) 100 parts by weight of solid rubber and (B) General formula [I] ▲There are numerical formulas, chemical formulas, tables, etc.▼[I] (However, in the formula, R_1 and R_2 are hydrogen , represents an alkyl group, a halogen, or a cyclopentenyl group, which may be the same or different, and in the above formula, hydrogen is bonded to at least two of the p-position and o-position with respect to the OH group. A cyclopentenylphenol compound shown in
A rubber composition containing 14,000 to 14,000.