GB2026497A

GB2026497A - Process for the preparation of a resin composition useful for laminated sheets

Info

Publication number: GB2026497A
Application number: GB7920459A
Authority: GB
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 1978-06-14
Filing date: 1979-06-12
Publication date: 1980-02-06
Also published as: NL7904672A; FR2428653A1; DE2924338A1; FR2428653B1; GB2026497B

Abstract

A resin composition is prepared by reacting a polybutadiene having a number average molecular weight of 150 to 10,000 and at least 80% 1,4- structure by weight with a phenol in the presence of an acid catalyst to obtain a composition which consists of a polybutadiene- phenol adduct and unreacted phenol, and reacting the polybutadiene- phenol adduct composition with formaldehyde or a formaldehyde precursor in the presence of a basic catalyst. The resin composition is useful for the preparation of laminated sheets, e.g. by impregnation of paper sheet or glass fibre cloth to form pepregs which are stacked together, optionally with copper foil at the top, and press-cured.

Description

SPECIFICATION Process for the preparation of a resin composition useful for laminated sheets The present invention relates to a process for the preparation of a novel resin composition comprising a phenol resin modified with a liquid polybutadiene, which is useful as a bonding agent for laminated sheets.

More particularly, it relates to a process for the preparation of a resin composition which comprises subjecting a phenol to an addition reaction with a liquid polybutadiene having at least 80 % 1,4-structure and a number average molecular weight of 150 to 10,000 and reacting the resulting resin with formaldehyde, said resin composition comprising a phenol resin modified with a liquid polybutadiene being useful as a bonding agent for laminated sheets, i.e. as a varnish for impregnating into base materials for laminated sheets, because of its excellent solubility in an organic solvent.The laminated sheet prepared by using the novel resin composition of the present invention as a bonding agent has excellent machinability, chemical resistance, curing characteristics and has various properties similar to or better than those of the conventional phenol resins modified with a drying oil. Furthermore, the resin composition of the present invention can be prepared at low cost.

Phenol resins have many excellent properties, such as water resistance, heat resistance and electrical characteristics, but are hard and brittle. Hence, they are usually not used alone, but are used in combination with other ingredients.

Laminated sheets are usually prepared by impregnating an uncured phenol resin into a base material such as paper, cotton cloth, asbestos paper, asbestos cloth or glass fiber cloth, drying the base material, laminating the impregnated base material resin and then applying heat and pressure to form a laminated sheet. Such laminated sheets are widely used as electrical insulating materials. Particularly, a phenolic paper laminated sheet having a thickness of from 0.8 to 3.2 mm is widely used for electrical devices, and a copper-clad laminate is used for a printed-wiring board. The latter copper-clad laminate is usually required to have excellent punchability at a low temperature, because when wire terminals of parts such as electrical resistances, diodes or condensors are inserted into punched holes in the sheets by an automatic insertion machine, high accuracy is required.In order to give the laminate sheet impact resistance, the laminate sheet is usually modified with a modifying agent such as a vegetable oil, an alkyl-phenol, or a polyether, by which flexibility is given to the laminate sheet. A representative example of such modifying agents is tung oil, but this is a natural product and is not only expensive but also variable in cost. Moreover, owing to the molecular structure of tung oil, laminated sheet modified with tung oil has inferior electrical characteristics.

Research has therefore been carried out to produce a synthetic drying oil which is useful as a modifying agent instead of tung oil. It has been proposed in Japanese Patent Publication (unexamined) No.79895/1973 and Japanese Patent Publication No. 43312/1972 to use as a modifying agent for a laminated sheet a methylol phenol resin obtained by subjecting a phenol to an addition reaction with a 1,2-type polybutadiene and then introducing thereto methylol groups. It has also been proposed in Japanese Patent Publication (unexamined) No. 109285/1975 to use a methylol phenol resin prepared by subjecting a phenol to an addition reaction with a polybutadiene containing about 40 % of vinyl group and then introducing thereto methylol groups.

However, when polybutadiene containing more than 20 % 1,2-structure, particularly more than 50 %, 1,2-structure is added to a phenol, a ring-forming reaction at the double bonds occurs vigorously with the assistance of an acid catalyst in addition to the addition reaction with the phenol, and hence, the resin obtained has a higher glass transition point and unfavourably low flexibility.

As a result of intensive study of the present inventors on liquid polybutadienes for improving the characteristics of phenolic laminated sheets, such as flexibility and electrical characteristics, it has been found that a liquid polybutadiene having at least 80 % 1,4structure can improve the characteristics particularly the flexibility of phenolic laminated sheet.

According to the present invention, a liquid polybutadiene having at least 80 % 1,4-structure and a number average molecular weight of from 150 to 10,000 is subjected to an addition reaction with a phenol in the presence of an acid catalyst to obtain a resin composition (A) comprising the addition product and the unreacted phenol, and then the composition (A) thus obtained is reacted with formaldehyde in the presence of a basic catalyst, the addition product of the liquid polybutadiene and the phenol contained in said composition (A) having one molecule of the phenol per 3 to 8 butadiene monomer units.

The liquid polybutadiene used in the present invention has at least 80 % 1,4-structure and a number average molecular weight of from 150 to 10,000, preferably from 600 to 2,000, (measured by vapor pressure osmometry), and has preferably a viscosity of 50 to 5,000 cps at 20or, more preferably 150 to 3,000 cps at 20"C, particularly 600 to 2,000 cps at 20"C, and an iodine value of 400 iodine/100 g or more. Such liquid polybutadienes can be prepared by conventional processes for example as disclosed in Japanese Patent Publications (unexamined) Nos. 43084/1973, 26396/1974 and 89788/1974.

The phenol used in the present invention includes, any monovalent or divalent phenols, such as phenol, cresol, xylenol, p-tert-butylphenol, resorcinol, nonylphenol, hydroquinone, catechol, saligenin, or the like, which may be used alone or as a combination of two or more thereof.

The composition (A) comprising the addition product of the liquid polybutadiene and the phenol is preferably prepared by adding the liquid polybutadiene all at once, or in portions to a mixture of an acid catalyst and the phenol, the phenol being used in an amount of from 10 to 1,000 parts by weight, preferably 50 to 400 parts by weight, per 100 parts of the liquid polybutadiene.

The resin composition (A) contains preferably the addition product of a specific ratio of the liquid polybutadiene and the phenol, i.e. one molecule of the phenol per 3 to 8 units of the butadiene monomer composing the liquid polybutadiene. For instance, in case of a liquid polybutadiene having a number average molecular weight of 1,200, it is preferable to add 2.8 to 7.4 molecules of the phenol per one molecule of the liquid polybutadiene. When the addition molecular number of the phenol is less than one molecule per 8 units of the butadiene monomer of the liquid polybutadiene, the resol product gives an uneven cured product consisting of two phases (uncured liquid polybutadiene-phenol adduct and solid phenol resin produced by curing of the methylol phenol) or a wholly uncured rubber-like product, on curing at 160for 20 minutes.Accordingly, when a laminated sheet is produced using such a resin composition, the curing speed is very low and hence the processing of the sheet is very difficult. On the other hand, when the addition molecular number of the phenol is more than one molecule per 3 units of the butadiene monomer of the liquid polybutadiene, the composition (A) has a very high viscosity, which results in inferior workability and poor impregnation of the base material and also inferior punchability of the laminated sheet.

The addition molecular number of phenol can be regulated within the suitable range by controlling the amount of the starting phenol and the reaction conditions such as reaction temperature and reaction time.

The acid catalyst used in the addition reaction includes protonic acids and Lewis acids. Suitable examples of the protonic acids are mineral acids such as sulfuric acid, hydrochloric acid, or the like, sulfonic acids such as p-toluenesulfonic acid or the like, or a mixture thereof, and suitable examples of Lewis acids are various Lewis acids or a complex thereof, such as aluminum chloride, ferric chloride, boron trifluoride, boron trifluoride-phenol complex, or mixture thereof. The amount of the acid catalyst is not critical, but it is usually used in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the liquid polybutadiene.

The addition reaction of the liquid polybutadiene and the phenol may optionally be carried out in the presence of a solvent. The solvent has preferably a dielectric constant of not higher than 15, more preferably not higher than 10, at 25"C. Suitable examples of the solvent are hydrocarbons such as benzene, toluene, xylene, n-heptane, n-hexane or cyclohexane; halogenated hydrocarbons such as monochlorobenzene, or dichlorobenzene, or the like. The solvent is preferably used in an amount of 5 to 500 parts by weight, more preferably 10 to 100 parts by weight, per 100 parts by weight of the liquid polybutadiene.

The reaction temperature of the addition reaction is not critical, but is preferably in the range of 40 to 170OC.

The formaldehyde may be in the form of a precursor such as formalin or paraformaldehyde. The formaldehyde or precursor is used in an amount of 0.6 to 3.0 mole, preferably 0.6 to 2.0 mole calculated as formaldehyde) per 1 mole of the phenol used for the preparation of the composition (A). When the formaldehyde is used in an amount of less than 0.6 mole, the methylol group-introducing reaction can not be carried out sufficiently, and hence, the laminated sheet prepared by using such a resin composition has inferior characteristics, i.e. inferior curing characteristics and inferior solvent resistance. On the other hand, when the solvent is used in an amount of more than 3.0 mole, the methylol group-introducing reaction proceeds too rapidly, and hence the reaction is impracticable.

The basic catalyst to be used in the reaction of the formaldehyde and the composition (A), i.e. in the methylol group-introducing reaction includes ammonia, amines, and hydroxides. Suitable examples of the amines are a primary amine of the formula: R-NH2 wherein R is a hydrocarbon group having 1 to 20 carbon atoms, such as an alkylamine having 1 to 20 carbon atoms in the alkyl moiety (e.g. methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, npentylamine, n-hexylamine or n-octylamine), a cycloalkylamine having 6 to 15 carbon atoms (e.g.

cyclohexylamine), an aralkylamine having 7 to 15 carbon atoms (e.g. benzylamine, or phenethylamine).

Examples of other amines are a dialkylamine having 1 to 20 carbon atoms in each alkyl moiety (e.g.

dimethylamine, diethylamine, or dipropylamine), a trialkylamine having 1 to 20 carbon atoms in each alkyl moiety (e.g. trimethylamine, triethylamine), an alkylenediamine having 2 to 5 carbon atoms in the alkylene moiety (e.g. ethylenediamine, or propylenediamine), trimethylolamine, hexamethylenetetramine, or the like.

Suitable examples of the hydroxides are an alkali metal hydoxide or alkaline earth metal hydroxide (e.g.

sodium hydroxide, potassium hydroxide, barium hydroxide). These basic compounds may be used alone or in a combination of two or more thereof.

In order to obtain a uniform and stable varnish which is prepared from the resin composition of the present invention and a solvent as described hereinafter, the primary amine of the formula: R-NH2 as mentioned above is preferably used alone or in a combination of other basic compounds. When the resin composition of the present invention is used for the preparation of a laminated sheets having high electrical insulating properties, ammonia or amines are preferable.

Amount of the basic catalyst is not critical, but it is usually used in an amount of 0.001 to 0.5 mole, preferably 0.01 to 0.5 mole, per 1 mole of the phenol used for the preparation of the composition (A). In case of the preparation of a uniform and stable varnish as mentioned above, the primary amine is preferably used in amount of 0.01 to 0.5 mole per 1 mol of the starting phenol, and when the primary amine is used together with other basic compounds, the primary amine is used in an amount of not less than 0.01 mole and total amount of the basic catalyst is up to 0.5 mole.

Other reaction conditions for the methylol group-introducing reaction are not critical, either, but the reaction is preferably carried out at a temperature of 60 to 120"C for 30 to 300 minutes, more preferably for 60 to 180 minutes. The reaction product may be used as a varnish for the preparation of a laminated sheet as it is, or after being dehydrated under reduced pressure and then being diluted with an appropriate solvent.

The methylol group-introducing reaction is preferably carried out in an appropriate solvent. The solvent includes hydrocarbons, halogenated hydrocarbons, alcohols, ethers, ketones, esters, or the like. Suitable examples of the hydrocarbons are benzene, toluene, xylene, durene, hexane, heptane, pentane, octane, or the like. Amontthem, benzene, toluene and xyiene are particularly preferable. Suitable examples of the halogenated hydrocarbons are monochlorobenzene, monobromobenzene, dichlorobenzene, dichloroethane, perchloroethylene, chlorohexane, chlorooctane, or the like.Alcohols are preferably include alcohols having 1 to 27 carbon atoms, for example, saturated monovalent alcohols such as methyl alcohol, ethylalcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, sec-amylalcohol, 1-ethylpropyl alcohol, isoamyl alcohol, tert-amyl alcohol, 2,2-dimethylpropyl alcohol, 1,2-dimethylpropyl alcohol, n-hexyl alcohol, 1,3-dimethyl-n-butyl alcohol, 1-methyl-n-hexyl alcohol, n-heptyl alcohol, 1-methyl-n-heptyl alcohol, n-octyl alcohol, capryl alcohol, 2-ethyl-n-hexyl alcohol, isooctyl alcohol, n-nonyl alcohol, n-decyl alcohol, n-undecyl alcohol, n-dodecyl alcohol, n-tridecyl alcohol, n-tetradecyl alcohol, n-pentadecyl alcohol, cetyl alcohol, stearyl alcohol, n-nonadecyl alcohol, behenyl alcohol, cyclohexanol, or the like; unsaturated monovalent alcohols such as allyl alcohol, pro-pargyl alcohol, crotyl alcohol, oleyl alcohol, elaidyl alcohol, linoleyl alcohol geraniol, or the like; aromatic alcohols such as benzyl alcohol, ss-phenylethyl alcohol, hydrocinnamyl alcohol, or the like; ether alcohols such as ethylene glycol monomethyl ether, ethylene glycol monethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, di-ethylene glycol monoethyl ether, triethylene glycol monomethyl ether, furfuryl alcohol, tetrahydrofurfuryl alcohol, or the like, which may be used alone or in a combination of two or more thereof.Although divalent alcohols such as ethylene glycol, diethylene glycol, propylene glycol, propanediol and butanediol may also be used, it is preferable to use an alcohol having a lower molecular weight because of ease of the removal thereof during the drying step of varnish.

Suitable examples of ethers are dimethyl ether, diethyl ether, dipropyl ether, tetrahydrofuran, or the like.

Suitable examples of ketones are acetone, diethyl ketone, dipropyl ketone, cyclohexanone, or the like.

Suitable examples of esters are ethyl formate, ethyl acetate, isoamyl acetate, ethyl butyrate, or the like.

Particularly preferred solvent is a mixture of 1 part by weight of a hydrocarbon as mentioned above and 0 to 100 parts by weight, more preferably 0 to 5 parts by weight, of an alcohol as mentioned above.

Amount of the solvent is not critical, but it is usually used in an amount of 1 to 2,000 parts by weight, preferably 20 to 500 parts by weight, per 100 parts by weight of the composition (A).

The present resin composition comprising a phenol resin modified with a liquid polybutadiene can be used for the production of laminated sheets by conventional methods. For example, the resin composition is firstly dissolved in an appropriate solvent to obtain a varnish, and the varnish thus prepared is impregnated into a base material and then dried to obtain a prepreg. Alternatively, the prepreg may be obtained by impregnating previously a prescribed amount of a water-soluble phenol resin and/or a phenol resin modified with an amine into a base material, drying the base material, and thereafter imprignating a prescribed amount of the resin composition of the present invention into the base material thus obtained and followed by drying. Necessary number of the prepreg thus prepared are piled up and pressed with heating to give the desired laminated sheet.

The solvent used for the preparation of a varnish includes the same solvents as used in the methylol group-introducing reaction as mentioned above, such as hydrocarbons, alcohols, ethers, ketones, and esters. Among them, toluene, methanol and acetones are preferable from the practical and economical viewpoints.

The base material used for the laminated sheet includes paper, cotton cloth, asbestos paper, asbestos cloth, glass fiber cloth, or the like. The base material is preferably subjected to the conventional surface treatment in order to improve the adhesion with the phenol resin modified with a liquid polybutadiene. For example, the glass fiber cloth containing no alkali is previously treated with silane or boran. When a plural of the prepregs are piled up and thereon a copper foil is piled and then the resulting piled product is heat-pressed, there can be obtained a copper-clad laminate.

The present invention is illustrated by the following Examples, but is not limited thereto.

Example 1 A mixture of phenol (150 g), toluene (50 g) and boron trifluoride-phenol complex (0.5 g) was heated at 70 75"C and thereto was added dropwise liquid polybutadiene (100 g), which had a viscosity of 660 cps at 20"C, a number average molecular weight of 1700 (measured by a vapor pressure osmometer), cis-1,4 structure of 74 %, trans-1 ,4 structure of 24 % and vinyl structure of 2 %, over a period of 20 minutes, and the mixture was reacted with agitation at 80"C for 2 hours. The reaction mixture was admixed with triethylamine (1.0 g) to obtain a resin composition (A1).

It was analytically confirmed that the resin composition (A1) was a mixture of a liquid polybutadienephenol adduct and unreacted phenol, in said adduct, 7.5 molecules of phenol in average being added to one molecule of the liquid polybutadiene (i.e. one molecule of phenol per 4.2 butadiene units).

To the resin composition (awl) (100 g) were added paraformaldehyde (20.8 g), hexamethylenetetramine (1.5 g), toluene (68 g) and isopropyl alcohol (32 g), and the mixture was reacted with agitation at 80 - 830C for 2 hours in a reactor. After the reaction, the reaction mixture was concentrated under reduced pressure. The concentrated mixture was dissolved in a mixed solvent of toluene-methanol (3:1 by weight) to give a homogeneous, transparent varnish of phenol resin modified with liquid polybutadiene which contained 50 % by weight of resin component.

A cotton linter paper was previously undercoated with a water-soluble phenol formaldehyde varnish and was impregnated with the varnish obtained above and dried to give a resin-impregnated base material (impregnated resin content: 45 % by weight).

Afixed number of the base material thus obtained was piled up and heat-pressed at 1600C under a pressure of 80 - 100 kg/cm2 for 50 minutes to give a laminated sheet having a thickness of 1.6 mm.

Example 2 To the same resin composition (A1) (100 g) as obtained in Example 1 were added paraformaldehyde (20.8 g), hexamethylenetetramine (3.0 g), toluene (52 g) and isopropanol (48 g). The mixture was reacted with agitation at 80 - 83"C for 2 hours in a reactor. After the reaction, the reaction mixture was concentrated under reduced pressure, and the concentrated mixture was dissolved in a mixed solvent of toluene-methanol (3:1 by weight) to give a homogeneous, transparent varnish of phenol resin modified with liquid polybutadiene which contained 50 % by weight of resin component. By using the vernish thus obtained, a laminated sheet having a thickness of 1.6 mm was prepared in the same manner as described in Example 1.

The properties of the varnishes and laminated sheets obtained in Examples 1 and 2 are shown in the following Table 1.

Table 1 Properties Example 1 Example 2 Appearance when the varnish was cured at 160"C for 20 Uniform, Uniform, minutes transparent transparent Gelling time of the varnish, i.e. time till the varnish was gelled when heated on a 6 minutes 7 minutes hot plate at 150"C Punchability of the laminated sheet at room temperature Very good Very good (ASTM D 617-70) Solvent resistance of the laminated sheet (the appearance was observed when Not changed Not changed immersed in boiling trichlenefor 10 minutes) Example 3 Liquid polybutadiene (100 g) (Sumikaoile &num;;150, a tradename of Sumitomo Chemical Company, Limited), which had a viscosity of 660 cps at 20"C, a number average molecular weight of 1700 (measured by a vapor pressure osmometer), cis-1 ,4 structure of 74 % trans-1,4 structure of 24 % and vinyl structure of 2 %, was mixed with phenol (150 g) and p-toluene-sulfonic acid (1.25 g). The mixture was reacted with agitation at 1OO0Cfor 2 hours, and thereto was added triethylamine (1.0 g) to obtain a resin composition (A2).

The resin composition (A2) was a mixture of a liquid polybutadiene-phenol adduct and unreacted phenol, in said adduct, 7.5 molecules of phenol in average being added to one molecule of the liquid polybutadiene (i.e. one molecule of phenol per 4.2 butadiene units), which was confirmed by a gas chromatography.

To the resin composition (A2) (100 9) were added paraformaldehyde (20.8 g), hexamethylenetetramine (1.5 g), toluene (60 g) and isopropyl alcohol (20 g), and the mixture was reacted with agitation at 80 - 83"C for 2 hours in a reactor. After reaction, the reaction mixture was concentrated under reduced pressure, and the concentrated mixture was dissolved in a mixed solvent of toluene-isopropyl alcohol (4:1 by weight) to obtain a homogeneous, transparent varnish of phenol resin modified with liquid polybutadiene which contained 50 % byweight of resin component.

A cotton linter paper, which was previously under-coated with a water-soluble phenol-formaldehyde varnish, was impregnated with the varnish obtained above and dried to give a resin-impregnated base material (impregnated resin content: 52 % by weight).

A fixed number of the base material thus obtained was piled up and heat-pressed at 1600C under a pressure of 80 - 100 kg/cm2 for 50 minutes to give a laminated sheet having a thickness of 1.6 mm.

Example 4 The same liquid polybutadiene (100 g) as used in Example 3 was mixed with phenol (150 g) and p-toluenesulfonic acid (0.75 g), and the mixture was reacted with agitation at 100 C for 2 hours, and to the reaction mixture was added triethylamine (0.6 g) to give a resin composition (A3).

It was confirmed by the same analysis as in Example 3 that in the liquid polybutadiene-phenol adduct contained in this resin composition (A3), 6.0 molecules of phenol were added to one molecule of the liquid polybutadiene (i.e. one molecule of phenol per 5.3 butadiene units).

The resin composition (A3) was reacted with formaldehyde in the same manner as described in Example 3, and the reaction mixture was concentrated under reduced pressure, and the concentrated mixture was dissolved in a mixed solvent of toluene-isopropanol (4:1 by weight) to give a homogeneous, transparent varnish of phenol resin modified with liquid polybutadiene which contained 50 % by weight of resin component.

A cotton linter paper, which was previously undercoated with a water-soluble phenol formaldehyde varnish, was impregnated with the varnish obtained above and dried to give a resin-impregnated base material (impregnated resin content: 47 % by weight).

A fixed number of the base material were piled up and heat-pressed at 160"C under a pressure of 80 - 100 kg/cm2 for 50 minutes to give a laminated sheet having a thickness of 1.6 mm.

Example 5 The same liquid polybutadiene (100 g) as used in Example 3 was mixed with phenol (150 g), p-toluenesulfonic acid (1.5 g) and toluene (50 g), and the mixture was reacted with agitation at 1 OO"C for 4 hours, and to the reaction mixture was added triethylamine (1.3 g) to give a resin composition (A4).

It was confirmed by the same analysis as in Example 3 that in the liquid polybutadiene-phenol adduct contained in the resin composition (A4), 8.0 molecules of phenol were added to one molecule of the liquid polybutadiene (i.e. one molecule of phenol per 3.9 butadiene units).

To the resin composition (A4) (100 9) were added paraformaldehyde (20.8 g), hexamethylenetetramine (1.5 g), toluene (43 g) and isopropyl alcohol (20 g), and the mixture was reacted with agitation at 80 - 830C for 2 hours in a reactor. After the reaction, the reaction mixture was concentrated under reduced pressure and the concentrated mixture was dissolved in a mixed solvent of toluene-isopropyl alochol (4:1 by weight) to give a homogeneous, transparentvarnish of phenol resin modified with liquid polybutadiene which contained 50 % by weight of resin component.

A cotton linter paper, which was previously undercoated with a water-soluble phenol formaldehyde varnish, was impregnated with the varnish obtained above and dried to give a resin-impregnated base material (impregnated resin content: 48 % by weight).

Afixed number of the base material were piled up and heat-pressed at 1600C under a pressure of 80 - 100 kg/cm2 for 50 minutes to give a laminated sheet having a thickness of 1.6 mm.

Reference Example 1 A liquid polybutadiene (100 g) (Nisso PB-B-1000, a tradename of Nippon Soda Co. Ltd.), which had a viscosity of 7400 cps at 20"C, a number average molecular weight of 1200 (measured by a vapor pressure osmometer), 1,2-vinyl structure of more than 85 % and 1,4-trans structure of less than 15 %, was mixed with phenol (150 g), p-toluenesulfonic acid (1.5 g), and toluene (50 g). The mixture was reacted with agitation at 100"C for 4 hours, and thereto was added triethylamine (1.3 g) to give a resin composition (A5).

It was confirmed by the same analysis as in Example 3 that in the liquid polybutadiene-phenol adduct contained in the resin composition (A5), 5.0 molecules of phenol in average were added to one molecule of liquid polybutadiene (i.e. one molecule of phenol per 4.4 butadiene units).

By using the resin composition (A5), a laminated sheet was prepared in the same manner as described in Example 3.

Reference Example 2 The same liquid polybutadiene (100 g) as used in Example 3 was mixed with phenol (150 g) and p-toluenesulfonic acid (1.25 g), and the mixture was reacted with agitation at 1 OO"C for 40 minutes, and thereto was added triethylamine (1.0 g) to give a resin composition (A6).

It was confirmed by the same analysis as in Example 3 that in the liquid polybutadiene-phenol adduct contained in the resin composition (A6), 2.1 molecules of phenol were added to one molecule of liquid polybutadiene (i.e. one molecule of phenol per 15 butadiene units).

By using the resin composition (A6) thus obtained, a laminated sheet was prepared in the same manner as described in Example 3.

Reference Example 3 The same liquid polybutadiene (100 g) as used in Example 3 was mixed with phenol (200 g) and p-toluenesulfonic acid (1.25 g), and the mixture was reacted with agitation at 1 OO"C for 8 hours, and thereto was added triethylamine (1.0 g) to give a resin composition (A7).

It was confirmed by the same analysis as in Example 3 that in the liquid polybutadiene-phenol adduct contained in the resin composition (A7), 11 molecules of phenol were as added to one molecule of liquid polybutadiene (i.e. one molecule of phenol per 2.8 butadiene units).

By using the resin composition (A7), a laminated sheet was prepared in the same manner as described in Example 3.

The properties of the varnishes and laminated sheets obtained in the above Examples 3 to 5 and Reference Examples 1 to 3 are shown in Table 2.

Table 2 Properties Example 3 Example 4 Example 5 Reference Reference Reference Example 1 Example 2 Example 3 Unevenly Appearance when the varnish cured was cured at 160 C for Uniformly Uniformly Uniformly Uniformly (non-cured Uniformly 20 minutes cured cured cured cured portions were cured observed) Gelling time of the varnish, i.e. time till the varnish longer longer was gelled when heated on 6 min. 8 min. 6 min. than than 4 min.

a hot plate at 150 C 15 min. 20 min.

Uneven Appearance of the laminated Very Very Very Very Surface due to sheet good good good good was tacky inferior impregnation *Solvent resistance to the laminated sheet (appearance Not Not Not Not was observed when immersed changed changed changed changed Blushing Blistering in boiling trichlene for 10 minutes) Cracking Cracking Punchability of the laminated was ob- was obsheet at room temperature Very Very Very served at Very served at (ASTM D 617-70) good good good punched good punched edges edges Example 6 A mixture of phenol (780 g), toluene (260 g) and boron trifluoride-phenol complex (2.6 ml) was heated at 70"C and thereto was added in portions with agitation a liquid polybutadiene (520 gY, which had a viscosity of 230 cps at 20"C, a number average molecular weight of 1110 (measured by a vapor pressure osmometer), cis-1,4 structure of 71 %, trans-1,4 structure of 26 % and vinyl structure of 3 %, over a period of 30 minutes, and the mixture was reacted with agitation at 80"C for 100 minutes, and thereto was added triethylamine (3.0 ml) in order to stop the reaction to give a resin composition (A8).

It was analytically confirmed that the resin composition (A8) was a mixture of a liquid polybutadienephenol adduct and unreacted phenol, and in the adduct, 4.8 molecules of phenol in average being added to one molecule of liquid polybutadiene (i.e. one molecule of phenol per 4.3 butadiene units).

The resin composition (A5) (1000 9) was mixed with paraformaldehye (207 g), n-butylamine (78 g), toluene (337 g) and isopropyl alcohol (135 g), and the mixture was reacted with agitation at 80 - 85"C for 3 hours (It was analytically confirmed that unreacted phenol was contained in the reaction mixture in an amount of less than 30 % by weight based on the total phenol used for the preparation of the resin composition). After the reaction, the reaction mixture was concentrated under reduced pressure and the concentrated mixture was dissolved in a mixed solvent of toluene-methanol (2:1 by weight) to give a varnish of a phenol resin modified with a liquid polybutadiene which contained 55 % by weight of non-volatile components.

By using the varnish thus obtained, a copper-clad laminate was prepared in the following manner. That is, a cotton linter paper, which was previously undercoated with a water-soluble phenol resin varnish, was impregnated with the varnish obtained above and dried to give a prepreg (impregnated resin content: 52 % by weight).

Eight sheets of the prepreg thus obtained were piled up and on the most outer sheet was piled a copper foil with an adhesive and the piled product was heat-pressed at 160"C under a pressure of 80 - 100 kg/cm2 for 50 minutes to give a copper-clad laminate having a thickness of 1.6 mm.

Example 7 The resin composition (A8) (1000 9) obtained in Example 6 was mixed with paraformaldehyde (207 g), hexamethylenetetramine (30 g), n-butylamine (19.5 g), toluene (377 g) and isopropyl alcohol (135 g), and the mixture was reacted with agitation at 80 - 85"C for 3 hours in a reactor (It was analytically confirmed that unreacted phenol was contained in the reaction mixture in an amount of less than 30 % by weight based on the total phenol used for the preparation of the resin composition). The reaction mixture was concentrated under reduced pressure and the concentrated mixture was dissolved in a mixed solvent of toluene-methanol (2:1 by weight) to give a varnish of the phenol resin modified with liquid polybutadiene which contained 55 % by weight of non-volatile components.

By using the varnish thus obtained, a copper-clad laminate was prepared in the following manner. That is, a cotton linter paper, which was previously undercoated with a water-soluble phenol resin varnish, was impregnated with the varnish obtained above and dried to give a prepreg (impregnated resin content: 55 % by weight).

Example 8 The resin composition (A6) (1000 9) obtained in Example 6 was mixed with paraformaldehyde (160 g), hexamethylenetetramine (15 g), n-butylamine (39 g), toluene (377 g) and isopropyl alcohol (135 g), and the mixture was reacted with agitation at 80 - 85"C for 3 hours in a reactor (It was analytically confirmed that unreacted phenol was contained in the reaction mixture in an amount of less than 30 % by weight based on the total phenol used for the preparation of the resin composition).The reaction mixture was concentrated under reduced pressure and the concentrated mixture was dissolved in a mixed solvent of toluene-methanol (2:1 by weight) to give a varnish of a phenol resin modified with liquid polybutadiene which contained 55 % by weight of non-volatile components.

By using the varnish thus obtained, a copper-clad laminate was prepared in the following manner. That is, a cotton linter paper, which was previously undercoated with a water-soluble phenol resin varnish, was impregnated with the varnish obtained above and dried to give a prepreg (impregnated resin content: 53 % by weight).

Eight sheets of the prepreg thus obtained was piled up and on the most outer sheet was piled a copper foil with an adhesive, and the piled product was heat-pressed at 1 600C under a pressure of 80 - 100 kg/cm2 for 50 minutes to give a copper-clad laminate having a thickness of 1.6 mm.

Example 9 The same liquid polybutadiene (480 g) as used in Example 6 was added in portions with agitation at 70"C to a mixture of phenol (530 g), toluene (240 g), boron trifluoride-phenol complex (2.4 ml) over a period of 30 minutes, and the mixture was reacted with agitation at 70"C for 80 minutes, and thereto was added triethylamine (3.0 ml) in order to stop the reaction to give a resin composition (Ag).

It was analytically confirmed that the resin composition (Ag) was a mixture of a liquid polybutadiene phenol adduct and unreacted phenol, and in the adduct, 4.6 molecules of phenol in average being added to one molecule of liquid polybutadiene (i.e. one molecule of phenol per 4.5 butadiene units).

The resin composition (Ag) (1000 g) thus obtained was mixed with paraformaldehyde (135 g), hexamethylenetetramine (12.5 g), n-butylamine (33 g), toluene (323 g) and isopropyl alcohol (129 g), and the mixture was reacted with agitation at 80 - 850C for 3 hours in a reactor (It was analytically confirmed that unreacted phenol was contained in the reaction mixture in an amount of less than 30 % by weight based on the total phenol used for the resin composition). The reaction mixture was concentrated under reduced pressure and the concentrated mixture was dissolved in a mixed solvent of toluene-methanol (3:1 by weight) to give a varnish of phenol resin modified with liquid polybutadiene which contained 55 % by weight of non-volatile components.

Eight sheets of the prepreg thus obtained were piled up and on the most outer sheet was piled a copper foil with an adhesive, and the piled product was heat-pressed at 160"C under a pressure of 80 - 100 kg/cm2 for 50 minutes to give a copper-clad laminate having a thickness of 1.6 mm.

Example 10 The same liquid polybutadiene (520 g) as used in Example 6 was mixed with phenol (780 g) and p-toluenesulfonic acid (3.9 g), and the mixture was reacted with agitation at 120"C for 2 hours and thereto was added triethylamine (2.0 ml) in order to stop the reaction to give a resin composition (A1O).

It was analytically confirmed that in a liquid polybutadiene-phenol adduct contained in the resin composition (A10), 4.3 molecules of phenol being added to one molecule of liquid polybutadiene (i.e. one molecule of phenol per 4.8 butadiene units).

The resin composition (also) was reacted with formaldehyde in the same manner as described in Example 6, and the reaction mixture was concentrated under reduced pressure and the concentrated mixture was dissolved in a mixed solvent of toluene-methanol (3:1 by weight) to give a varnish of a phenol resin modified with a liquid polybutadiene which contained 55 % by weight of non-volatile components.

Reference Example 4 The same liquid polybutadiene (520 g) as used in Example 6 was added in portions with agitation at 700C to a mixture of phenol (780 g), toluene (260 g) and boron trifluoride-phenol complex (2.6 ml) over a period of 30 minutes and the mixture was reacted with agitation at 70"C for 20 minutes and to the reaction mixture was added triethylamine (3.0 ml) in order to stop the reaction to give a resin composition (A,,).

It was analytically confirmed that in a liquid polybutadiene-phenol adduct contained in the resin composition (All), 2.1 molecules of phenol being added to one molecule of the liquid polybutadiene (i.e. one molecule of phenol per 10 butadiene units).

In the same manner as described in Example 6, a varnish of a phenol resin modified with a liquid polybutadiene was prepared by using the resin composition (All) obtained above.

Reference Example 5 The same liquid polybutadiene (520 g) as used in Example 6 was added in portions with agitation at 70"C to a mixture of phenol (780 g), toluene (260 g) and boron trifluoride-phenol complex (5.2 ml) over a period of 30 minutes, and the mixture was reacted with agitation at 95"C for 180 minutes, and to the reaction mixture was added triethylamine (6.0 ml) in order to stop the reaction to give a resin composition (A12).

It was analytically confirmed that in the liquid polybutadiene-phenol adduct contained in the resin composition (A,2), 8.2 molecules of phenol being added to one molecule of the liquid polybutadiene (i.e. one molecule of phenol per 2.5 butadiene units).

In the same manner as described in Example 6, a varnish of a phenol resin modified with a liquid polybutadiene was prepared by using the resin composition (at2) obtained above, and further a copper-clad laminate was prepared by using the varnish thus obtained.

The properties of the varnishes and copper-clad laminates obtained in the above Examples 6 to 10 and Reference Examples 4 and 5 are shown in the following Table 3 and 4. The properties of the copper-clad laminates were measured as follows: (1) Dielectric dissipation factor, dielectric constant, water absorption, trichlene resistance and flexural strength .... in accordance with the provision of JIS C-6481.

(2) Punchability.... in accordance with the provision of ASTM D-617-70.

Table 3 Example No. Stability ofg Gelling time"2 Curing'3 varnish characteristics Example 6 Not changed 5 minutes Uniformly for more than cured 21 days Example 7 ,, Example 8 " " " Example 9 ,, 6minutes Example 10 Not changed for more than 14 days Reference Separated into more than Unevenly cured Example 4 two layers 15 minutes (non-cured portions after 2 days were observed) Reference Not changed Shorter than Uniformly Example 5 for more than 3 minutes cured 21 days [Remarks]: *1) The varnishes (non-volatile components: 55 % by weight) were allowed to stand at 15 20 C, and the appearance thereof was observed.

*2) Times till the varnishes were gelled when heated on a hot plate at 150 C.

*3) The varnishes were cured by heating at 1600C for 20 minutes and then the appearance thereof was observed.

Table 4 Properties Example 6 Example 7 Example 8 Example 9 Example 10 Reference Example 5 Dielectric C-90/20/65 0.0322 0.0344 0.0342 0.0290 0.0356 0.0342 dissipation factor C-90/20/65 (1 MHZ) + D-48/50 0.0463 0.0482 0.0518 0.0478 0.0533 0.0855 Dielectric C-90/20/65 4.450 4.605 4.562 4.030 4.841 4.505 constant (1 MHZ) C-90/20/65 + D-48/50 5.040 5.274 5.214 4.674 5.601 6.122 Water E-24/50+ absorption D-24/23 0.43% 0.41% 0.48% 0.43% 0.47% 1.1% Trichlene Boiled for Not Not Not Not Not Not resistance 5 minutes changed changed changed changed changed changed Flexural strength (in horizontal (kg/mm) 15.6 15.7 15.2 13.0 15.0 10.0 direction) Punchability ASTM Very Very Very Very (at 50-70 C) D-617-70 good good good Excellent good bad Example 11 A mixture of phenol (150 g), toluene (50 g) and boron trifluoride-phenol complex (0.5 g) was heated at 70 75"C and thereto was added dropwise a liquid polybutadiene (100 g) having a viscosity of 290 cps at 20"C, a number average molecular weight of 1230 (measured by a vapor pressure osmometer), cis-1 4 structure of 71 %, trans-1 ,4 structure of 26 % and vinyl structure of 3 % over a period of 20 minutes, and the mixture was reacted with agitation at 80"C for 2 hours, and thereafter, triethylamine (1.0 g) was added to the reaction mixture to give a resin composition (A,3).

It was analytically confirmed that the resin composition (at3) was a mixture of a liquid polybutadienephenol adduct and unreacted phenol, and in the adduct, 5.5 molecules of phenol in average being added to one molecule of liquid polybutadiene.

The resin composition (at3) (100 g) was mixed with paraformaldehyde (16.0 g) hexamethylenetetramine (3.0 g), toluene (64 g) and isopropyl alcohol (16 g), and the mixture was reacted with agitation at 80 - 83"C for 2 hours in a reactor. After the reaction, the reaction mixture was concentrated under reduced pressure and the concentrated mixture was dissolved in a mixed solvent of toluene-methanol (3:1 by weight) to give a homogeneous, transparent varnish of a phenol resin modified with a liquid polybutadiene which contained 50 % by weight of resin component.

A glass fiber cloth was impregnated with a 1 % aqueous solution of a hydrolyzed product of y-aminopropyl-ethoxysilane and dried. The glass fiber cloth thus treated was impregnated with the varnish obtained above and dried to give a resin-impregnated base material (impregnated resin content: 55 % by weight).

Afixed number of the base material thus obtained were piled up and on one side thereof was piled a copper foil with adhesive, and the resulting piled product was heat-pressed at 1600C under a pressure of 80 100 kg/cm2 for 50 minutes to give a copper-clad laminate having a thickness of 1.6 mm.

Example 12 The resin composition (100 g) as obtained in Example 11 was mixed with paraformaldehyde (16.0 g), hexamethylene-tetramine (1.5 g), n-butylamine (8.0 g), toluene (64 g) and isopropyl alcohol (16 g), and the mixture was reacted with agitation at 80 - 830C for 2 hours in a reactor. After the reaction, the reaction mixture was concentrated under reduced pressure to give a homogeneous, transparent varnish of a phenol resin modified with a liquid polybutadiene which contained 50 % by weight of resin component. By using the varnish, a copper-clad laminate having a thickness of 1.6 mm was prepared in the same manner as described in Example 11.

Reference Example 6 A mixture of phenol (150 g) and p-toluenesulfonic acid (0.150 g) was heated at 70 - 75"C and thereto was added dropwise Chinese tung oil (100 g) having a viscosity of 280 cps at 20"C and a number average molecular weight of 870 (measured by a vapor pressure osmometer) over a period of 20 minutes, and the mixture was reacted with agitation at 80"C for 2 hours, and thereto was added triethylamine (1.0 g) to give a composition (A,4).

It was analytically confirmed that the composition (A4) was a mixture of a tung oil-phenol adduct, and in the adduct, 3.2 molecules of phenol in average being added to one molecule of chinese tung oil.

The composition (at4) (100 g) was mixed with formalin (65.0 g) and a 28 % aqueous ammonia (4.0 g), and the mixture was reacted with agitation at 80 - 83"C for 2 hours in a reactor. After the reaction, the reaction mixture was concentrated under reduced pressure and the concentrated mixture was dissolved in a mixed solvent of toluene-methanol (1 1 1 by weight) to give a homogeneous, transparent varnish of a phenol resin modified with tung oil.

By using the varnish thus obtained, a copper-clad laminate was prepared in the same manner as described in Example 11.

The properties of the copper-clad laminates obtained in Examples 11 and 12 and Reference Example 6 were measured. The results are shown in Table 5.

Table 5 Properties Example 11 Example 12 Reference Example 6 Dielectric C-90/20/65 0.020 0.025 0.035 dissipation factor C-90/20/65 (1 MHZ) + D-48/50 0.033 0.035 0.047 Dielectric C-90/20/65 4.50 4.50 4.97 constant (1 MHZ) C-90/20/65 + D-48/50 4.60 4.70 4.98 Water E-24/50 + absorption D-24/23 0.10% 0.15% 0.30% Trichlene Boiled for Not Not Not resistance 5 minutes changed changed changed Punchability ASTM Very Very Very (at80"C) D-617-70 good good good

Claims

1. A process for the preparation of a resin composition, which comprises reacting a polybutadiene having a number average molecular weight of 150 to 10,000 and at least 80 % by weight 1,4-structure with a phenol in the presence of an acid catalyst to obtain a composition of a polybutadiene-phenol adduct wherein one molecule of phenol per 3 to 8 butadiene units is added to the polybutadiene, and reacting the polybutadiene-phenol adduct composition with formaldehyde or a formaldehyde precursor in the presence of a basic catalyst.

2. A process according to claim 1, wherein the acid catalyst is used in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the polybutadiene.

3. A process according to claim 1 or claim 2, wherein the phenol is used in an amount of 10 to 1,000 parts by weight per 100 parts by weight of the polybutadiene.

4. A process according to claim 3, wherein the amount of the phenol is in the range of 50 to 500 parts by weight per 100 parts by weight of the polybutadiene.

5. A process according to any one of claims 1 to 4, wherein the polybutadiene has a number average molecular weight of 600 to 2,000.

6. A process according to any one of claims 1 to 5, wherein the reaction of the polybutadiene and the phenol is carried out by adding the polybutadiene to a mixture of the phenol and an acid catalyst.

7. A process according to any one of claims 1 to 6, wherein the acid catalyst is sulfuric acid, hydrochloric acid, p-toluenesulfonic acid, aluminum chloride, ferric chloride, boron trifluoride, or boron trifluoride-phenol complex.

8. A process according to any one of claims 1 to 7, wherein the phenol is phenol, cresol, xylenol, p-tert-butylphenol, resorcinol, nonylphenol, hydroquinone, catechol, or saligenin.

9. A process according to any one of claims 1 to 8, wherein the reaction of the polybutadiene and the phenol is carried out in a solvent which is a hydrocarbon or a halogenated hydrocarbon, and which has a dielectric constant of not higher than 15 at 25"C.

10. A process according to claim 9, wherein the solvent is used in an amount of 5 to 500 parts by weight per 100 parts by weight of the polybutadiene.

11. A process according to claim 10, wherein the amount of the solvent is from 10 to 100 parts by weight per 100 parts by weight of the polybutadiene.

12. A process according to claim 1, wherein the reaction of the polybutadiene and the phenol is carried out at a temperature of 40 to 170"C.

13. A process according to any one of claims 1 to 12, wherein the formaldehyde is used in an amount of from 0.6 to 3.0 mole per mole of the phenol used for the preparation of the polybutadiene-phenol adduct composition.

14. A process according to claim 13, wherein the amount of formaldehyde is from 0.6 to 2.0 mole per mole of the phenol used for the preparation of the polybutadiene-phenol adduct composition.

15. A process according to any one of claims 1 to 14, wherein the basic catalyst is an amine, ammonia or a metal hydroxide.

16. A process according to claim 15, wherein the basic catalyst is a primary amine of the formula: R-NH2 wherein R is a hydrocarbon group having from 1 to 20 carbon atoms.

17. A process according to any one of claims 1 to 16, wherein the basic catalyst is used in an amount from 0.001 to 0.5 mole per mole of the phenol used for the preparation of the polybutadiene-phenol adduct composition.

18. A process according to claim 17, wherein the amount of the basic catalyst is from 0.01 to 0.5 mole per mole of the phenol used for the preparation of the polybutadiene-phenol adduct composition.

19. A process according to any one of claims 13 to 18, wherein the reaction of the polybutadiene-phenol adduct composition and the formaldehyde or formaldehyde precursor is carried out in a solvent which is a hydrocarbon, a halogenated hydrocarbon, an alcohol, an ether, a ketone or an ester or a mixture of two or more thereof.

20. A process according to claim 19, wherein the solvent consists of one part by weight of a hydrocarbon and from 0 to 100 parts by weight of an alcohol.

21. A process for the preparation of a resin composition such as hereinbefore described in any one of the Examples.

22. A resin composition prepared by a process as claimed in any one of the preceding claims.

23. A process for preparing a laminated sheet which process comprises impregnating a base material with a resin composition as claimed in claim 22 to give a prepreg, drying the prepreg, layering a plurality of prepregs thus obtained and then applying heat and pressure to produce a laminated sheet.

24. A process according to claim 23, wherein the base material is a paper, a cotton cloth, an asbestos paper, an asbestos cloth or a glass fiber cloth.

25. A process according to claim 23 or 24 wherein a layer of a copper foil is included before the application of heat and pressure.

26. A process for the preparation of a laminated sheet substantially as hereinbefore described in any one of the foregoing specified Examples.

27. A laminated sheet produced by a method as claimed in any one of claims 23 to 26.