JPH0816212B2 - Polyvinyl acetal resin for adhesives - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyvinyl acetal resin for adhesives, which has excellent heat resistance and is suitable for use as, for example, an adhesive for laminated boards of printed circuits.

(Prior Art) A polyvinyl acetal resin typified by polyvinyl butyral resin and a thermosetting resin typified by a phenol resin or an epoxy resin are used as an adhesive composition.
It has been widely used as an adhesive for laminated plates.

A laminated board is usually formed by laminating a copper foil on the upper surface of a phenol resin-impregnated paper via an adhesive and heating and pressurizing this, and printing the copper foil on the surface of this copper-clad laminated board by etching. The substrate is created.

In recent years, such printed circuit boards tend to be immersed in a solder bath for a long time and the circuit density tends to increase with the weight reduction and miniaturization of various electric appliances. Therefore, even as an adhesive used for the laminated plate, further excellent heat resistance is required compared with the conventional one, and it is particularly desired to improve the “peel strength” of the copper foil at high temperature. ing.

Therefore, JP-A-57-3802 proposes to improve the heat resistance of the polyvinyl acetal resin itself by adjusting the ratio of the acetalized portion with acetaldehyde and the acetalized portion with butyraldehyde. Japanese Patent Publication No. 47-47574 proposes an adhesive composition containing a polyvinyl acetal resin, a phenol formaldehyde resin, and an organic phosphorus compound.

(Problems to be Solved by the Invention) However, in any of the above-mentioned adhesive compositions, it cannot be said that the above-mentioned demand for higher heat resistance is still sufficient. is there.

The present invention has been made by focusing on the above situation,
Its purpose is heat resistance, especially "solder heat resistance".
Another object of the present invention is to provide a polyvinyl acetal resin for adhesives, which is excellent in “peeling strength”.

(Means for Solving the Problems) The polyvinyl acetal resin for adhesives of the present invention is a polyvinyl acetal resin for adhesives obtained by condensing two or more aldehydes containing at least acetaldehyde and furfural and polyvinyl alcohol. The total acetalized portion (A) + (B) + in the resin
The proportion of (C) is 65 to 87% by weight, the total proportion of the acetalized portion (A) with acetaldehyde and the acetalized portion (B) with furfural is 85% by weight or more of the total acetalized portion, and The ratio of the acetalized portion (B) due to furfural to the whole resin is 0.1
˜4% by weight, and has a structure represented by the following general formula (1) (A); Acetalized part with acetaldehyde (B); Acetalized part with furfural (C); Acetalized part with other aldehydes (A) + (B) + (C); Total acetalized part (D); The reaction is characterized by the polyvinyl alcohol moiety (E); the vinylacetyl moiety R; the moiety other than the aldehyde group in the other aldehyde, thereby achieving the above object.

The polyvinyl alcohol used in the present invention preferably has a degree of polymerization of 1000 to 3000, more preferably 1500.
~ 2500. When polyvinyl alcohol having a degree of polymerization of more than 3000 is used, the viscosity of the adhesive prepared as described below becomes too high, which is not practical. Also,
When polyvinyl alcohol having a degree of polymerization of less than 1000 is used, the adhesiveness of the adhesive at high temperature tends to decrease.

In the present invention, two or more aldehydes including at least acetaldehyde and furfural are used as the aldehyde. In addition to the two aldehydes, furfural and acetaldehyde, other aldehydes may be used in small amounts. As the other aldehyde, an aldehyde used in the production of a conventionally known polyvinyl acetal resin, which is generally known, is used. Preferred examples thereof include alkyl aldehydes having 1 to 8 carbon atoms such as formaldehyde, propionaldehyde, butyraldehyde, 2-ethylbutyraldehyde, 2-ethylhexylaldehyde,
Examples thereof include cyclohexyl aldehyde, glyogizal, glutaraldehyde, benzaldehyde and phenyl aldehyde.

The ratio of all acetalized moieties (A) + (B) + (C) acetalized with each of the above aldehydes is 65 to 87% by weight relative to the total amount of polyvinyl acetal resin,
It is preferably 70% by weight. When the ratio of the total acetalized portion (A) + (B) + (C) is less than 65% by weight, heat resistance, especially peel strength between the obtained adhesive and the above-mentioned copper foil is insufficient. Become. Therefore, the proportion of all acetalized moieties (A) + (B) + (C) in the resin is 65 to 87% by weight, preferably 70% by weight.

Further, the total ratio of the acetalized portion by furfural and acetaldehyde is 85% of the total acetalized portion.
It is considered to be more than weight%. When this ratio is less than 85% by weight of the total acetalized portion (A) + (B) + (C), the above-mentioned furfural and aldehydes other than acetaldehyde exceed 15% by weight of the total amount of the acetalized portion. Therefore, there is a possibility that the crosslinking reaction due to the furfural ring may be hindered, and that the furfural acetalization reaction itself may be difficult to proceed.

Furthermore, an acetalization part (B) by furfural
The ratio of the resin to the whole resin is 0.1 to 4% by weight, preferably 0.2 to 2% by weight. If the proportion of the acetalized portion (B) due to furfural with respect to the entire resin is less than this range, the self-crosslinking reaction due to furfural is less likely to occur, and the solder heat resistance tends to decrease.
If the proportion of the acetalized portion (B) due to furfural with respect to the entire resin is higher than the above range, the self-crosslinking reaction due to furfural will proceed excessively, resulting in deterioration of flexibility and reduction in peel strength of the copper foil. It is in.

The polyvinyl acetal resin for adhesives can be obtained by condensing polyvinyl alcohol and aldehyde by an acetalization reaction that has been conventionally used. For example, after adding an acid catalyst to an aqueous solution of polyvinyl alcohol, an aldehyde such as furfural and acetaldehyde is added thereto and reacted to precipitate the polyvinyl acetal resin thus produced, or polyvinyl alcohol is dispersed in an organic solvent to obtain an acid catalyst. A dissolution method or the like in which the aldehyde compound and the aldehyde compound are added and reacted can be adopted. As the catalyst, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and hydrosulfuric acid, and organic acids such as organic sulfonic acid can be used.

To further explain the precipitation method for obtaining the polyvinyl acetal resin of the present invention, generally, polyvinyl alcohol is dissolved in warm water and then cooled, and after reaching a predetermined temperature, an acid catalyst and an aldehyde such as furfural and acetaldehyde are appropriately added. throw into. The order of adding each aldehyde is not limited. For example, furfural may be added to the above solution to carry out the acetalization reaction, and then acetaldehyde and other aldehydes may be added as necessary, or acetaldehyde and other aldehydes may be added first. After the solution is first charged into the solution to carry out the acetalization reaction, furfural may be added thereto, or further, aldehydes such as furfural and acetaldehyde may be simultaneously charged into the solution to carry out the acetalization reaction. Especially, it is better to put furfural first
It is preferable in terms of control of resin particles. An acetalized product is deposited by this acetalization reaction. Then, the reaction system is kept at a relatively high temperature for a predetermined time for aging, and then the acid catalyst is neutralized and washed with water to remove the catalyst and unreacted aldehyde, and then purified and dried by a conventional method. A polyvinyl acetal resin for adhesives is obtained.

Using the polyvinyl acetal resin for an adhesive thus obtained, for example, in order to prepare an adhesive for a laminated board, the resin may be used alone, or may be another thermoplastic resin or a thermoplastic resin. You may use together with curable resin. As the thermosetting resin, phenol resin, epoxy resin, urea resin, melamine resin, urethane resin, etc. are preferably used.
You may use these individually or in combination. The mixing ratio of the polyvinyl acetal resin and the thermosetting resin is 1: 4 by weight.
The range of 4: 1 is preferable, and 2: 3 to 3: 2 is particularly preferable.

In addition, the adhesive for laminates is blended with a solvent capable of dissolving the above resin, and for the purpose of improving heat resistance and other reasons, additives such as antioxidant and defoaming agent are blended as necessary. May be done. As the solvent, those generally used for adhesives can be used, and for example, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol, ethanol and butanol, and aromatic hydrocarbons such as toluene and xylene are suitable. Used.

Thus, as described above, the polyvinyl acetal resin obtained by condensing the polyvinyl alcohol with furfural and acetaldehyde, which are aldehydes having self-crosslinking property by heating, increases the bonding force between the resins by crosslinking the resins with each other by heating, It is possible to improve “solder heat resistance” and “peel strength”. The cross-linking by the furfural ring does not cause deterioration in electric properties as seen in addition of carboxylic acid, and can obtain preferable results when the obtained polyvinyl acetal resin is blended in an adhesive for laminates. Further, since the crosslinking reaction by the furfural ring is an addition reaction, not a condensation reaction, a volatile matter such as water is not generated during the reaction as seen in the condensation reaction, and a good adhesive layer is obtained. be able to.

(Example) Hereinafter, the present invention will be described in detail based on examples.

Example 1 Preparation of Polyvinyl Acetal Resin 2750 g of pure water was placed in the separable flask of 5, and polyvinyl alcohol (polymerization degree 2400, residual acetyl group
220 g (2.7 wt%) was added and completely dissolved. Next, the liquid temperature of this solution was maintained at 25 ° C., and 580 g of 35 wt% hydrochloric acid was added to it.
Then, 10 g of furfural was added, the liquid temperature was lowered to 10 ° C., and 154 g of acetaldehyde was appropriately added to precipitate a colorless powder. Then, the temperature of the reaction system was raised to 45 ° C., and the temperature was maintained at this temperature for 5 hours, then neutralized and washed with water to remove the catalyst and unreacted aldehyde, and then dried to obtain a polyvinyl acetal resin.

Preparation of adhesive for laminated board 50 g of polyvinyl acetal resin obtained above, 55 g of phenol resin (PL-2205 manufactured by Gunei Chemical Co., Ltd.), and 7 g of epoxy resin (Epicoat 828 manufactured by Shell Chemical Co., Ltd.)
Was dissolved in 340 g of a mixed solvent (acetone / MEK / toluene = 1/1/1) to prepare an adhesive for laminated plates.

Next, this adhesive for laminates was applied to a copper foil for printed boards (thickness 35 μm) as a solid content so as to have a thickness of 33 μm, and dried at 140 ° C. for 4 minutes to obtain a copper foil with an adhesive. This copper foil and phenol resin impregnated paper at 150 ℃ for 40 minutes, 120kg
A copper clad laminate was prepared by pressure molding under the condition of / cm ² .

The "solder heat resistance" and the "peeling strength" of the obtained copper-clad laminate were measured according to JIS C-6481.

The test temperature is 260 ° C for "solder heat resistance".
"Peeling strength" is 20 ℃ and 150 ℃
I went to each. The degree of acetalization is measured by JI
The measurement was performed according to the measurement of vinyl butyral described in S K6728.

At this time, a sample of polyvinyl acetal was reacted with hydroxylamine hydrochloride, and the resulting hydrochloric acid was titrated to obtain a sample.
The number of moles of hydrochloric acid generated per gram was calculated as the total number of moles of polyvinyl acetal per gram of sample.

On the other hand, by gas chromatographic analysis using the same sample, the ratio of the number of moles of each free aldehyde produced by the decomposition of acetaldehyde, furfural, and other acetals was determined as the composition ratio (molar ratio) to the total amount of the free aldehydes. The number of moles of each polyvinyl acetal per 1 g of the sample was calculated as the ratio of the number of moles of the free aldehyde of 1 = the number of moles of each polyvinyl acetal to the number of moles of all polyvinyl acetals.

Further, the number of moles of vinyl acetyl moiety per 1 g of the sample was determined from the saponification degree of the raw material polyvinyl alcohol.

The weight% of each component was calculated from the number of moles of each component per 1 g of the sample obtained by the above method.

Examples 2-5 and Comparative Examples 1-4 As shown in Table 1-1, the amount of acetaldehyde, furfural and other aldehydes, and the same procedure as in Example 1 were used except that the aldehydes were used in different amounts. An adhesive was obtained to make a copper clad laminate. The “solder heat resistance” and “peel strength” of each copper clad laminate were tested in the same manner as in Example 1. The degree of acetalization of the mixed polyvinyl acetal resin was calculated by the same method as in Example 1. The results are summarized in Tables 1-1 and 1-2.

From the results in the above table, when the proportion of furfural was increased as in Comparative Example 1, when furfural was not used as in Comparative Example 2, and as in Comparative Example 3, acetaldehyde and an aldehyde other than furfural (in this case, , Butyraldehyde) was used in a large amount, and the proportion of all acetalized moieties was the same as in Comparative Example 4.
When the content was less than 65% by weight, the soldering heat resistance was poor and the peeling strength of the copper foil was also low in the test results of the laminates. On the other hand, in the laminates using the adhesive for laminates of Examples 1 to 5, satisfactory results were obtained for both solder heat resistance and peel strength.

(Effect of the invention) As described above, in the present invention, the proportion of all acetalized moieties (A) + (B) + (C) in the resin is 65 to 87% by weight,
The total proportion of the acetalized portion (A) with acetaldehyde and the acetalized portion (B) with furfural is 85% by weight or more of the total acetalized portion, and the proportion of the acetalized portion (B) with furfural to the whole resin is 0.1 to 4% by weight, the following general formula (1)
Has a structure represented by (A); Acetalized part with acetaldehyde (B); Acetalized part with furfural (C); Acetalized part with other aldehydes (A) + (B) + (C); Total acetalized part (D); Polyvinyl alcohol part (E) of reaction; vinyl acetyl part R; part other than aldehyde group in other aldehydes, so that solder heat resistance can be improved and peeling strength of copper foil can be increased, and solder heat resistance can be improved. It is possible to obtain an adhesive for laminates, which has excellent properties and peel strength.

Claims (1)

[Claims] 1. A polyvinyl acetal resin for adhesives, which is obtained by condensing two or more kinds of aldehydes containing at least acetaldehyde and furfural with polyvinyl alcohol, wherein the proportion of all acetalized moieties in the resin is 65 to 87. % By weight, the total proportion of the acetalized portion with acetaldehyde (A) and the furfural acetalized portion (B) is 85% by weight or more of the total acetalized portion, and the furfural acetalized portion (B). A polyvinyl acetal resin for an adhesive, which has a structure represented by the following general formula (1) in a proportion of 0.1 to 4% by weight based on the whole resin. (A); Acetalized part with acetaldehyde (B); Acetalized part with furfural (C); Acetalized part with other aldehydes (A) + (B) + (C); Total acetalized part (D); Polyvinyl alcohol part of reaction (E); Vinyl acetyl part R; Part other than aldehyde group in other aldehydes