JPH0834961A - Polyvinyl acetal resin and adhesive composition using the same polyvinyl acetal resin - Google Patents

Abstract

PURPOSE:To obtain a polyvinyl acetal resin having excellent heat resistance, especially soldering resistance and hot peel strength and an adhesive composition using the same polyvinyl acetal resin. CONSTITUTION:This polyvinyl acetal resin is obtained by acetalizing two kinds of polyvinyl alcohols having different degrees of polymerization. The degree of one polyvinyl acetal resin is 200-1,000 and that of the other is 3,000-9,000. The adhesive composition contains the polyvinyl acetal resin and a thermosetting resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl acetal resin which is excellent in heat resistance and peel strength and is suitable for use as an adhesive for printed circuit boards and the like, and an adhesive composition using the polyvinyl acetal resin.

[0002]

2. Description of the Related Art An adhesive composition containing a polyvinyl acetal resin typified by polyvinyl butyral resin and a thermosetting resin typified by phenol resin, epoxy resin, melamine resin or the like as main components is used for printed circuit boards. Conventionally, it has been widely used as an adhesive. The printed circuit board is usually a copper-clad laminate comprising a copper foil, a phenol resin-impregnated paper, and an adhesive for adhering them, and by etching the copper on the surface of the copper-clad laminate. , A printed circuit board on which a desired printed circuit is formed.

In recent years, various electronic devices, electric devices and the like have been in the trend of weight reduction and miniaturization, and accordingly, demands for miniaturization of printed circuit boards and high density of printed circuits have increased. . As a result, the solder bath dipping time when mounting components on the printed circuit board is long, and higher performance than before is required for the adhesive used for the printed circuit board. Demands for excellent heat resistance and peel strength to withstand immersion in a solder bath, especially for peel strength under heat, are increasing.

Various attempts have been made to meet the above-mentioned requirements, for example, the degree of polymerization is 2500 to 3000.
Adhesive composition comprising a polyvinyl acetal resin obtained by reacting polyvinyl alcohol with an aldehyde and a thermosetting resin (JP-A-55-27342), and acetoacetal having a degree of polymerization of 1500 to 2500. -Butyl acetal-mixed polyvinyl acetal, wherein the weight ratio of the acetoacetal part and the butyl acetal part is 3: 7 to 7: 3, the vinyl alcohol part is 14 to 21% by weight, and the vinyl acetal part is 3%.
An adhesive for laminates of printed circuits containing polyvinyl acetal as a main component in an amount of less than or equal to wt. Polyvinyl acetal resin for adhesives in which the proportion of the acetalized portion is about 85 to 100% by weight based on the total acetalized portion (Japanese Patent Laid-Open No. 6-58242).
No. 3-301208) is proposed.

However, since the adhesives and polyvinyl acetal resins for adhesives as proposed above are still insufficient in heat resistance, they cannot withstand the recent prolonged immersion in a solder bath and are not practical. There is a problem of lacking.

[0006]

In order to solve the above-mentioned conventional problems, the present invention uses a polyvinyl acetal resin excellent in heat resistance, particularly solder heat resistance and peel strength under heat, and the polyvinyl acetal resin. It is an object to provide an adhesive composition.

[0007]

A polyvinyl acetal resin according to the invention of claim 1 (hereinafter referred to as "first invention") is a polyvinyl acetal resin obtained by acetalizing two kinds of polyvinyl alcohols having different degrees of polymerization. And the degree of polymerization of one polyvinyl alcohol is 20
The degree of polymerization of the other polyvinyl alcohol is from 3000 to 9000, whereby the above object is achieved.

The adhesive composition according to the invention of claim 2 (hereinafter referred to as "second invention") is characterized by containing the polyvinyl acetal resin according to the first invention and a thermosetting resin. Therefore, the above object is achieved.

The polyvinyl acetal resin according to the first invention has a degree of polymerization of 200 to 1000 and a degree of polymerization of 3000 to 3000.
It is obtained by reacting two kinds of polyvinyl alcohol of 9000 and aldehydes to form an acetal.

The types of the above-mentioned aldehydes are not particularly limited, but formaldehyde, acetaldehyde, paraacetaldehyde, propionaldehyde, butyraldehyde, alkyl aldehydes such as 2-ethylhexyl aldehyde, aromatic aldehydes such as benzaldehyde, and cyclohexyl. Aldehyde, glyoxal, glutaraldehyde, furfural, etc. are mentioned, and these 1 type (s) or 2 or more types are used suitably.

In the polyvinyl acetal resin according to the first invention, the degree of polymerization is 200 to 1000 and the degree of polymerization is 3.
It is necessary to use two kinds of polyvinyl alcohol of 000 to 9000. The degree of saponification of the above-mentioned two kinds of polyvinyl alcohol is not particularly limited, but is preferably 85 mol% or more.

When the degree of polymerization of the polyvinyl alcohol having a degree of polymerization of 200 to 1000 (hereinafter referred to as "PVA (L)") is less than 200, the polyvinyl acetal resin and the adhesive composition obtained have heat resistance and peel strength. In particular, when the peel strength at the time of heating becomes insufficient and the degree of polymerization exceeds 1,000 on the contrary, the obtained polyvinyl acetal resin and adhesive composition do not sufficiently flow into the fine irregularities of the metal foil surface, and the peel strength And heat resistance will be insufficient.

Polyvinyl alcohol having a degree of polymerization of 3000 to 9000 (hereinafter referred to as "PVA (H)")
If the degree of polymerization is less than 3000, the heat resistance of the solder becomes insufficient as in the case of an adhesive composition using a conventional polyvinyl acetal resin, and conversely, if the degree of polymerization exceeds 9000, a polyvinyl acetal resin is obtained. And, the solution viscosity of the adhesive composition becomes too high, a uniform coating thickness cannot be obtained, and the flow into the fine irregularities on the surface of the metal foil becomes insufficient, resulting in insufficient peel strength and heat resistance. Become.

The combined ratio of PVA (L) and PVA (H) is not particularly limited, but the weight ratio of PVA (L) and PVA (H) is not limited.
(L) / PVA (H) = 0.05 to 4 is preferable, and 0.2 to 3 is more preferable.

By weight ratio, PVA (L) / PVA (H) =
When it is less than 0.05, the solution viscosity of the obtained polyvinyl acetal resin and the adhesive composition becomes too high, so that a uniform coating thickness cannot be obtained, and the inflow into the fine irregularities of the metal foil surface is also impaired. It becomes sufficient and peel strength and heat resistance become insufficient. Conversely, PVA (L) / PVA in weight ratio
If (H) = 4 is exceeded, the solution viscosity of the obtained polyvinyl acetal resin and adhesive composition becomes too low, and it becomes difficult to obtain a uniform predetermined coating thickness, and the peel strength, solder heat resistance, etc. are significantly reduced. To do.

The content of the acetal group in the polyvinyl acetal resin according to the first invention is not particularly limited, but is preferably 60 to 80 mol%, and more preferably 65 to 78 mol%. Is more preferable.

If the acetal group content is less than 60 mol%, the solubility in organic solvents and the compatibility with thermosetting resins will decrease, leading to poor coatability, peel strength, solder heat resistance, etc. Will be insufficient. Conversely, the acetal group content is 80 mol%
If it exceeds, the peel strength of the obtained adhesive composition, especially the peel strength at the time of heat, the heat resistance of solder, etc., becomes insufficient.

In the polyvinyl acetal resin according to the first invention, the residual acetyl group content is not particularly limited, but is preferably 10 mol% or less, and more preferably 5 mol% or less. Is more preferable. When the residual acetyl group content exceeds 10 mol%,
The heat resistance of the obtained adhesive composition decreases.

The polyvinyl acetal resin according to the first invention comprises a polyvinyl alcohol having a polymerization degree of 200 to 1000 and a polyvinyl alcohol having a polymerization degree of 3000 to 9000.
It is obtained by using various kinds of polyvinyl alcohol and reacting with the above aldehydes to form an acetal.

The method of the acetalization reaction is not particularly limited. For example, a precipitation method in which an acid catalyst is added to an aqueous solution of polyvinyl alcohol, and then an aldehyde is added and reacted to precipitate a polyvinyl acetal resin produced May be used, or polyvinyl alcohol is dispersed in an organic solvent, an acid catalyst and aldehydes are added,
After the reaction, a dissolution method may be used in which a poor solvent is added to the obtained polyvinyl acetal resin solution or the obtained polyvinyl acetal resin solution is dispersed in the poor solvent to obtain polyvinyl acetal resin powder.

The acid catalyst is not particularly limited, but examples thereof include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, and organic acids such as acetic acid and organic sulfonic acid. One of these is used. Alternatively, two or more kinds are preferably used.

The polyvinyl acetal resin according to the first invention comprises a polyvinyl alcohol having a polymerization degree of 200 to 1000 and a polyvinyl alcohol having a polymerization degree of 3000 to 9000.
The polyvinyl alcohols of various kinds may be mixed in advance at a predetermined ratio and then reacted with aldehydes to be acetalized, or polyvinyl acetate having a polymerization degree of 200 to 1000 and polyvinyl acetate having a polymerization degree of 3000 to 9000 may be used. Two kinds of polyvinyl acetate, which are polyvinyl acetate, may be mixed in advance at a predetermined ratio, saponified with an acid or an alkali to give polyvinyl alcohol, and then reacted with aldehydes to be acetalized.

The adhesive composition according to the second invention comprises the polyvinyl acetal resin according to the first invention and a thermosetting resin dissolved in an organic solvent.

The type of the thermosetting resin is not particularly limited, and examples thereof include phenol resin, epoxy resin, urea resin, melamine resin, urethane resin and the like, and one or more of these may be used. It is preferably used.

The mixing ratio of the polyvinyl acetal resin according to the first invention and the thermosetting resin is not particularly limited, but the polyvinyl acetal resin / thermosetting resin = 1/4 to 4 by weight ratio. It is preferably / 1, and more preferably 2/3 to 3/2.

When the weight ratio of polyvinyl acetal resin / thermosetting resin is less than 1/4, the cured film of the obtained adhesive composition becomes too hard and brittle, and the peel strength decreases. Conversely, polyvinyl acetal resin / thermosetting resin =
When it exceeds 4/1, the cured film of the obtained adhesive composition becomes too soft and the heat resistance is lowered.

The kind of the organic solvent used in the adhesive composition according to the second invention is not particularly limited as long as it can uniformly dissolve the polyvinyl acetal resin according to the first invention and the thermosetting resin. Although not a thing, alcohols such as methanol, ethanol, butanol, ketones such as acetone and methyl ethyl ketone, toluene,
Examples thereof include aromatic hydrocarbons such as xylene, and one or more of these are preferably used.

The adhesive composition according to the second aspect of the invention may contain a heat stabilizer, if necessary, within a range that does not impair the object of the invention.
Various additives such as an antioxidant, an ultraviolet absorber and an antifoaming agent may be contained.

[0029]

The polyvinyl acetal resin according to the first invention is
Since it is obtained by acetalizing two kinds of polyvinyl alcohols having different degrees of polymerization with aldehydes, the adhesive composition according to the second invention containing the polyvinyl acetal resin and the thermosetting resin has excellent heat resistance. Combines peel strength.

[0030]

EXAMPLES In order to explain the present invention in more detail, examples will be given below.

(Example 1)

(A ) Preparation of polyvinyl acetal resin 3600 g of pure water was placed in a 5 l separable flask, and as shown in Table 1, 81 g of polyvinyl alcohol having a degree of polymerization of 800 (saponification degree of 98.6 mol%) and a degree of polymerization of 4000. 176g of polyvinyl alcohol (saponification degree 98.4mol%)
Was added and mixed by stirring at 80 ° C. to completely dissolve it. At this time, the total amount of polyvinyl alcohol was 257 g, and the weight ratio of the low polymerization degree polyvinyl alcohol and the high polymerization degree polyvinyl alcohol was 0.460. Then, the liquid temperature of this aqueous solution was cooled to 50 ° C., and hydrochloric acid (35% by weight) 2
30 g was added, the liquid temperature was lowered to 35 ° C., 60 g of paraacetaldehyde was added, and the temperature was kept at 25 to 30 ° C. for 3 hours. When the liquid temperature was further cooled to 15 ° C. and 79 g of butyraldehyde was added and reacted, a white powdery polyvinyl acetal resin was precipitated and precipitated. After completion of the reaction, the resin solution was neutralized, washed with water, filtered and dried to obtain a polyvinyl acetal resin. The polyvinyl acetal resin thus obtained had an acetal group content of 72 mol% and a residual acetyl group content of 1.5 mol%.

( B) Preparation of Adhesive Composition 40 g of the polyvinyl acetal resin obtained above, 62 g of phenol resin (trade name "PL-2205", manufactured by Gunei Chemical Co., Ltd.) and epoxy resin (trade name "Epicoat 82"
8 ", manufactured by Yuka Shell Epoxy Co., Ltd.) was dissolved in 258 g of a mixed solvent of acetone / methyl ethyl ketone / toluene = 2/2/1 (weight ratio) to obtain an adhesive composition.

( C) Evaluation The adhesive composition obtained above was applied to a copper foil for a printed circuit board having a thickness of 35 μm so that the film thickness after drying would be 33 μm, and dried at 140 ° C. for 4 minutes, A copper foil with an adhesive layer was obtained. Next, the copper foil with the adhesive layer and the phenol resin-impregnated paper were heat-bonded at 150 ° C. for 30 minutes while applying a pressure of 120 kg / cm ² to obtain a single-sided copper-clad laminate having a thickness of 2 mm.

Table 2 shows the results of evaluation of various performances of the single-sided copper-clad laminate obtained as described above by the following methods.

Solder heat resistance : JIS C-6481
In accordance with "Test method for copper clad laminate for printed wiring board", 2
The time (seconds) until swelling occurred in a 60 ° C. solder bath was measured.

Peel strength (20 ° C.) : JIS C-64
According to 81, peel strength at 20 ° C (kg / cm)
Was measured.

Peel strength (150 ° C.) : JIS C-6
Peel strength (kg / c
m) was measured.

(Examples 2 to 9)

As shown in Table 1, eight kinds of polyvinyl acetal resins were obtained in the same manner as in Example 1 by combining two kinds of polyvinyl alcohol and aldehydes.

Using the obtained 8 kinds of polyvinyl acetal resins, 8 kinds of adhesive compositions were prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 2. there were.

(Comparative Examples 1 to 6)

As shown in Table 1, six kinds of polyvinyl acetal resins were obtained in the same manner as in Example 1 by combining one kind of polyvinyl alcohol and aldehydes.

Using the resulting 6 types of polyvinyl acetal resins, 6 types of adhesive compositions were prepared in the same manner as in Example 1, and the results of evaluation in the same manner as in Example 1 are shown in Table 2. there were.

[0045]

[Table 1]

[0046]

[Table 2]

As shown in Tables 1 and 2, the adhesive compositions of Examples 1 to 9 containing the polyvinyl acetal resin obtained by using two kinds of polyvinyl alcohols having different degrees of polymerization in combination were excellent. Solder heat resistance and 20 ℃ and 150
Combines high peel strength at ℃. On the other hand, the adhesive compositions of Comparative Examples 1 to 6 containing the polyvinyl acetal resin obtained by using one kind of polyvinyl alcohol are inferior in both solder heat resistance and peel strength at 20 ° C and 150 ° C.

[0048]

As described above, the second invention containing the polyvinyl acetal resin according to the first invention and the thermosetting resin is used.
The adhesive composition according to the present invention has excellent solder heat resistance and high peel strength under normal conditions and heat conditions, and thus is suitable for use as an adhesive for printed circuit boards and the like.

Claims (2)

[Claims] 1. A polyvinyl acetal resin obtained by acetalizing two kinds of polyvinyl alcohols having different degrees of polymerization, wherein one polyvinyl alcohol has a polymerization degree of 200 to 1000 and the other polyvinyl alcohol has a polymerization degree of 3000. The polyvinyl acetal resin is characterized by being ˜9000. 2. An adhesive composition comprising the polyvinyl acetal resin according to claim 1 and a thermosetting resin.