JPH0791421B2 - Synthetic rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a synthetic rubber composition using an aromatic petroleum resin having a special structure as a tackifier. More specifically, an aromatic petroleum resin, which is a polymer in which an aromatic ring is bound through a methylene group and has no double bond and oxygen atom, or which is practically not used, is used as a tackifier. The present invention relates to a synthetic rubber composition having excellent adhesiveness and aging resistance.

(Prior Art) In general, rubber products have an important processing department for laminating and molding thin sheets of unvulcanized rubber during the manufacturing process. In this process, the tackiness of the unvulcanized rubber sheet is an important factor controlling the processability. Synthetic rubber such as SBR is inferior in adhesiveness to natural rubber, so it is necessary to add a tackifier to give adhesiveness to the adhesive surface.

Such a tackifier is required to have a function of being well compatible with synthetic rubber and increasing the tackiness of the composition, and also not to have a bad influence on the vulcanizability and the chemical / physical properties of the vulcanized rubber. Is desired.

As a synthetic rubber composition having a tackifying function, conventionally,
Alkylphenol-acetylene condensates, alkylphenol-formaldehyde condensates, alkylphenol-based resins such as alkylphenol-sulfide resins, xylene resins, coumarone-indene resins, petroleum resins, etc. are used.

(Problems to be Solved by the Invention) Of these tackifiers used in synthetic rubber compositions, alkylphenol resins and xylene resins have relatively good tackifying effects, but are extremely expensive. There is. On the other hand, coumarone-indene resin and petroleum resin are inferior in tackifying effect, but they are cheap and have softening property, so that they are used as a softening agent and a bulking agent when tackiness is not a serious problem. Further, tackifiers for these synthetic rubber compositions, including alkylphenol-based resins and xylene resins, have a functional group with high chemical reactivity in the molecule due to their chemical structure, and therefore are not inevitable in terms of aging resistance. The current situation is that satisfactory performance has not been obtained.

As described above, a single tackifier is not industrially satisfactory in terms of both price and performance, and two or more of these tackifiers are mixed with a synthetic rubber composition depending on the application. There are many cases.

Petroleum resins include C ₅ (aliphatic) petroleum resins, C ₉ (aromatic) petroleum resins, and C ₅ -C ₉ copolymer petroleum resins. These petroleum resins are inexpensive and stable in supply, and because they have the property of imparting softening properties to synthetic rubber, they can be used as a bulking agent and have excellent properties as a synthetic rubber composition. However, as described above, there are disadvantages that the tackifying effect is small and the aging resistance is not sufficient.

The tackifying effect is considered to be manifested when the tackifier is compatible with the synthetic rubber and unravels the synthetic rubber molecules.Therefore, improvement is expected by selecting a petroleum resin with a low molecular weight and a narrow molecular weight distribution range. it can.

Further, the cause of the poor aging resistance is presumed to be due to a highly reactive functional group present in the molecule of the petroleum resin, that is, a double bond. Therefore, for the purpose of eliminating or reducing double bonds, a method of secondary hydrogenation of petroleum resin (for example,
Japanese Patent Publication 55-41635, Japanese Publication 54-20972, Japanese Publication 45-17075
Etc.) has been implemented and is marketed under the general name of hydrogenated petroleum resin. However, the hydrogenation reaction of petroleum resin generally requires severe hydrogenation conditions, so that an increase in manufacturing cost is unavoidable, and hydrogenation does not improve the tackifying effect.

(Means for Solving Problems) From the above consideration, in order to obtain a synthetic rubber composition having excellent tackiness and aging resistance, a tackifier used in the synthetic rubber composition should have a functional group such as a double bond. It can be seen that a petroleum resin which does not have a group and has a low molecular weight and a narrow molecular weight distribution width for its softening point and which can be generally produced is demanded.

The present inventors have a drawback of conventional synthetic rubber compositions using petroleum resins. As a result of diligent research to improve aging resistance and tackiness, compatibility and aging resistance are improved by using a new type of petroleum resin that meets the above conditions, that is, an aromatic petroleum resin having a special structure. To find a synthetic rubber composition that provides excellent tackiness and satisfactory tackiness,
The present invention has been reached.

That is, the present invention is a polymer having a form in which an aromatic ring or a fraction containing an aromatic compound as a main component and formaldehyde are reacted in the presence of an acid catalyst to form an aromatic ring bonded through a methylene group. Therefore, it is a synthetic rubber composition containing an aromatic petroleum resin having no double bond and no oxygen atom or containing no oxygen atom practically as an essential component of a tackifier. The double bond does not include a double bond of an aromatic ring.

The above aromatic petroleum resin used as a tackifier in the present invention, its structure, compared with the conventional C ₉ petroleum resins, the compatibility of the distribution width of the molecular weight of the synthetic rubber narrower at low molecular weight,
Excellent in tackifying effect. Further, since it does not contain a highly reactive functional group in the molecule, it has excellent chemical resistance and aging resistance.

Furthermore, the petroleum resin has the advantage that it can be produced in a single step and is inexpensive, and that it can be used as an extender because it has softening properties. Therefore, the synthetic rubber composition of the present invention can utilize the characteristics of the aromatic petroleum resin as it is and, at the same time, adversely affect the vulcanizability and the chemical / physical properties of the vulcanized rubber as described later. There is no.

(Operation) The aromatic petroleum resin used in the present invention can be produced by reacting an aromatic compound or a fraction containing an aromatic compound as a main component with formaldehyde in the presence of an acid catalyst. First, as an aromatic raw material, a benzene ring such as toluene, xylene, ethylbenzene, methylethylbenzene, trimethylbenzene, durene, or indurene is substituted with 1 to 4 substituents having a relatively small carbon number such as a methyl group or an ethyl group. There is no particular limitation as long as it is a derivative of various condensed polycyclic aromatic compounds such as benzene derivative and indane derivative, naphthalene and anthracene, a mixture thereof or a fraction containing a part thereof. Even if an aromatic compound having a substituent having a relatively large number of carbon atoms such as a propyl group or a butyl group or a non-aromatic compound such as paraffin or naphthene is contained, these compounds are not reactive with formaldehyde. Since it is low or does not exist at all, it merely acts as a solvent, and the yield of the resin on the ascending process decreases, but there is no particular problem if the above-mentioned reactive aromatic compound is contained in the feed oil. . However, it is necessary to consider the content of the reactive aromatic compound in the feedstock when determining the molar ratio of formaldehyde to the feedstock described below. Thus, generally, toluene, a reforming-type or cracking-type mixed xylene fraction, a C ₉ or C ₁₀ aromatic fraction obtained from a bottom oil of xylene production or isomerization, etc. are practically preferable feedstocks. .

Formaldehyde, which is one of the starting materials, may be in any form as a starting material as long as it produces monomeric formaldehyde in the reaction system. For example, commercially available various concentrations of formalin or trioxane or paraformaldehyde. Although such a polymer as described above can be used as it is, paraformaldehyde, which does not lower the catalyst concentration (formalin reduces the catalyst concentration because it is an aqueous solution) and is easily available at a bottom price, is most suitable.

Further, it is also possible to dissolve gaseous formaldehyde separately generated by some method in a raw material oil, a catalyst (in the case of a liquid), a solvent and the like and charge it in the reaction system.

The catalyst is not particularly limited as long as it is an acid catalyst, and sulfuric acid, phosphoric acid,
Pyrophosphoric acid, perchloric acid, aluminum chloride, boron trifluoride, etc. can be used. Sulfuric acid is advantageous because it is cheap and easy to reuse. The solvent is not particularly necessary because an excess amount of the raw material oil acts as a solvent, but an appropriate amount of a solvent that does not participate in the reaction (eg, isoparaffin) can be added if necessary.

In order to obtain an aromatic petroleum resin containing neither oxygen atom nor double bond, the molar ratio of formaldehyde to reactive aromatic compound needs to be suppressed to 1 or less, preferably 0.8 or less. Depending on the type of aromatic compound used as the raw material, generally, the lower the molar ratio, the lower the yield of the produced petroleum resin and the lower the softening point. The content can be decreased, and the higher the molar ratio, the higher the yield and the softening point, but the higher the content of oxygen atoms. Although it is possible to produce a petroleum resin even when the molar ratio is greater than 1, the content of oxygen atoms becomes high and the catalyst separation operation becomes difficult under the practical reaction conditions described below.

The amount of the catalyst used in this reaction cannot be unconditionally specified because it is closely related to the reaction conditions, but generally 5 to 50% by weight, preferably 15 to 50% by weight based on the reactive aromatic compound in the feed oil.
35% by weight is suitable.

The reaction temperature of this reaction depends on the type and amount of the feed oil and the catalyst, and therefore cannot be specified unconditionally.
60 to 180 ° C, preferably 80 to 120 ° C is used.

The reaction time related to this reaction cannot be specified unconditionally because it depends on the type and amount of the feed oil and the catalyst, and the oxygen content of the petroleum resin produced decreases with the reaction time. Can be regarded as not containing at all,
The time to decrease to 0.1% by weight or less, generally 0.5 to 10 hours, preferably 2 to 5 hours is used.

Catalyst removal of reaction products, washing (removal of trace acidic substances),
The desired aromatic petroleum resin is obtained by removing unreacted oil, solvent (when used) and light products.

The final distillation conditions cannot be unconditionally specified because it depends on the type of feed oil and the required properties of the target aromatic petroleum resin, but it is usually under a reduced pressure of 5 mmHg or less, preferably under a reduced pressure of 2 mmHg or less. The target aromatic petroleum resin is obtained by distilling off light components at a temperature of 300 to 470 ° C or lower.

The aromatic petroleum resin thus obtained is mainly composed of an oligomer having an aromatic ring and a methylene group alternately bonded to each other and having an aromatic ring or a methyl group at a terminal, and has no double bond or oxygen atom. Since it has no or practically no content, it has a higher softening point than conventional C ₉ petroleum resins, but has a low molecular weight and a narrow molecular weight distribution, so it has high compatibility with synthetic rubber and a large tackifying effect. . Here, having no double bond, or not containing at all practically means having a bromine number of 1.0 or less, and having no oxygen atom or not containing at all practically 0.1% by weight of oxygen. It means the following.

The synthetic rubber used in the present invention is not particularly limited as long as it is a synthetic rubber compatible with the aromatic petroleum resin, but generally, SBR, alfin rubber, IIR, BR,
CR, NBR, EPOM, etc., preferably SBR can be used.

In the synthetic rubber composition of the present invention, the aromatic petroleum resin and the synthetic rubber can be mixed in a compounding ratio according to the purpose. The mixing method can be carried out by various known methods without particular limitation. The compounding ratio of aromatic petroleum resin and synthetic rubber is 1: 100.
50: 100 (weight ratio), preferably 2: 100 to 20: 100 (weight ratio), and if necessary, a filler, a pigment, a softening agent, a processing agent, an accelerator, an antiaging agent, etc. It can also be added in a compounding ratio. Further, the aromatic petroleum resin can be mixed with a conventional tackifier at an arbitrary mixing ratio and used.

(Examples) Examples will be shown below for clarifying the contents of the present invention, but the present invention is not limited to these examples unless the gist thereof is exceeded.

In the practice, the softening point and bromine number of the produced aromatic petroleum resin were measured according to JIS K-2207 and JIS K-2605, respectively, and the oxygen content was measured by an elemental analyzer. It was confirmed by elemental analysis, infrared spectroscopic analysis, nuclear magnetic resonance analysis, vapor pressure equilibrium method (VPO) analysis, and structural analysis by gel permeation chromatography that the aromatic ring was an oligomer bound through a methylene group. .

Next, Reference Examples 1 to 4 show the method for producing the aromatic petroleum resin used in the present invention.

Reference Example 1 240 g of a C ₉ aromatic fraction having a boiling range of 150 to 180 ° C. of a reforming bottom oil of xylene in a four-necked flask equipped with a stirrer and a reflux condenser and 20 g of commercial industrial 92% paraformaldehyde. Then, 75 g of commercially available dilute sulfuric acid (75%) was added dropwise with slow stirring. After adding sulfuric acid, adjust the reaction temperature to 100 using an oil bath.
The temperature was raised to ~ 110 ° C and the reaction was continued for 3 hours with vigorous stirring. After completion of the reaction, the mixture was cooled to room temperature, and the contents were transferred to a dropping funnel and left to stand, so that a sulfuric acid layer was separated into a lower layer, which was removed.

Subsequently, washing with water was repeated 2-3 times until the pH of the washing water showed 7. Transfer the resulting oil layer to a distillation flask, initially about 10 mm
Finally, the pressure reduction degree was raised to 1 mmHg by vacuum distillation of Hg to remove light components below 360 ° C. at atmospheric pressure, and 134 g of the target aromatic petroleum resin was obtained in the bottom of the kettle. The obtained petroleum resin has a softening point of 88.5 ° C, a bromine number of 0.2g Br ₂ / 100g, and an oxygen content of
It was 0.1% by weight or less, and it was clarified that neither oxygen atom nor double bond was contained practically.

Reference Example 2 Using the same equipment as in Reference Example 1, reaction and removal of catalyst under the same conditions and washing with water were carried out, and finally, under a reduced pressure of 1 mmHg, light components below 460 ° C. at atmospheric pressure were distilled off. Then, 112 g of a target aromatic petroleum resin was obtained. The resulting softening point of the petroleum resin is 117.5 ° C., Bromine Number 0.3g Br ₂ / 100g, oxygen Motoritsu was 0.1% by weight or less.

Reference Example 3 Using the same apparatus as in Reference Example 1 and using 240 g of xylene fraction as a raw material under the same conditions as in Reference Example 1, reaction, removal of catalyst and washing with water were carried out, and then a light fraction at a pressure of 340 ° C. or lower at atmospheric pressure was obtained. After removal by distillation under reduced pressure, 107.4 g of the target aromatic petroleum resin was obtained.

The petroleum resin obtained has a softening point of 65.5 ° C and a bromine number of 0.2 g Br.
_The oxygen content was less than 0.1% by weight.

Reference Example 4 Under the same conditions as in Reference Example 1, using the same apparatus as in Reference Example 1 and using 240 g of xylene fraction as a raw material, the reaction, catalyst removal and washing with water were carried out, and then a light fraction at 450 ° C. at atmospheric pressure was obtained. After removal by distillation under reduced pressure, 98.2 g of the desired aromatic petroleum resin was obtained.

The petroleum resin obtained has a softening point of 92.0 ° C and a bromine number of 0.2 g Br ₂
/ 100g, the oxygen content was less than 0.1% by weight.

Examples 1 to 4 and Comparative Examples 1 to 2 In order to carry out the evaluation as a synthetic rubber composition, first, the aromatic petroleum resins (respectively referred to as Resins 1 to 4) produced in Reference Examples 1 to 4 and a comparison were compared. The conventional commercially available aromatic petroleum resin (softening point 100 ° C.) and commercially available coumarone indene resin (softening point 90 ° C.) used were used as tackifiers to prepare synthetic rubber compositions having the compounding ratios shown in Table 1. The preparation was carried out by an ordinary method using an ordinary rubber kneading mixer.

Next, a compatibility test and a peeling test showing tackiness were performed. For compatibility, a part of the synthetic rubber composition after kneading was applied on a glass plate and the appearance was observed. In addition, the peeling test is applied to No. 11 canvas three times, dried for 24 hours, and then pressure-bonded with hand rolls twice, and after 48 hours, a load of 20 kg is applied for 1 minute to pressure-bond, and a Shopper-type tensile test is performed. The maximum load was obtained by pulling it off with a machine at a pulling speed of 320 mm / min.

The test results are shown in Table 2.

Next, a vulcanization test was carried out. Vulcanization conditions are 150 ° C for 20 minutes and 6
It is vulcanized by hot pressing for 0 minutes to prepare a No. 3 type dumbbell test piece conforming to JIS K-6301, and using a Shopper type tensile tester at a pulling speed of 500 mm / min, 100%, 300%, 500% modulus and tensile strength. Then, the elongation was measured.

The hardness was measured by a spring type hardness tester after vulcanization for 60 minutes.

The test results are shown in Table 3.

Finally, an aging test was conducted. The 100% modulus, the tensile strength and the elongation of the No. 3 dumbbell test piece after aging at 120 ° C. for 100 hours and the test piece before aging were measured.

The residual rate was calculated according to the following formula.

The test results are shown in Table 4.

(Effects of the Invention) The synthetic rubber composition of the present invention is one in which an aromatic petroleum resin having a special structure is blended as a tackifier, and is excellent in tackiness, vulcanizing time and properties of the vulcanized rubber. Has no adverse effect and has excellent aging resistance.

Front Page Continuation (56) References JP-B-44-21214 (JP, B1) JP-B-40-1955 (JP, B1) JP-B 38-18232 (JP, B1) JP-B 37-679 (JP , B1)

Claims (3)

[Claims] 1. An aromatic petroleum resin, which is a polymer in which an aromatic ring is bonded through a methylene group and has no double bond and no oxygen atom, or which does not contain practically at all, is an essential component. Synthetic rubber composition. 2. A synthetic rubber is styrene-butadiene rubber (SB
The synthetic rubber composition according to claim 1, which is R). 3. An aromatic petroleum resin is a polymer obtained by reacting an aromatic compound or a fraction containing an aromatic compound as a main component with formaldehyde in the presence of an acid catalyst. The synthetic rubber composition described.