JPS5917144B2 - glue - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adhesive, particularly an adhesive having excellent heat resistance, for printed circuit laminates, and to an improved adhesive based on polyvinyl acetal.

Generally, printed circuit laminates are manufactured by coating copper foil with an adhesive, drying it to form an adhesive-coated copper foil, and heat-pressing the adhesive-coated copper foil with a resin-impregnated base material. These copper-clad laminates are etched to create electrical circuits, and circuit parts are attached to them for use in various electronic devices. Copper-clad laminates require strong adhesion to bond metal copper and non-conductive substrates, but they also require etching, soldering when attaching circuit components, and especially in recent years. The trend of immersing products in high-temperature solder baths for long periods of time has progressed, and products with excellent heat resistance have become required. Therefore, improvements have been made to resin-impregnated base materials and copper plates, but improvements to the adhesive itself are also required.
In order to improve this type of adhesive, attempts have been made to add a new ro component or to improve the blending ratio.

Amino resins such as polyvinyl acetal, phenolic resins, epoxy resins, and melamine, and isocyanate resins are used, and among them, polyvinyl acetal is one of the important adhesive components. Further, in JP-A-55-34250, the use of polyvinyl acetal with a degree of polymerization of 2,000 to 3,000 has been proposed, and attempts have also been made to improve phenolic resins. The present invention is intended to improve polyvinyl acetal itself, which is the main component of adhesive compositions for copper-clad laminates.

As a method for improving polyvinyl acetal used as a solute, JP-A-55-27342 discloses a method in which polyvinyl alcohol has a degree of polymerization of 2,500 to 3,000, and a mixture of at least two types of formaldehyde 25, acetaldehyde, and butyraldehyde is used. Acetals are disclosed. However, according to research by the present inventors, the higher the degree of polymerization of polyvinyl acetal, the faster the high temperature adhesion.
However, when it exceeds 2,500, solvent solubility and workability decrease, making it unsuitable for practical use.

Even if it is a mixed acetal of acetoacetal and butyl acetal with a low polymerization degree of 2500 or less, when the weight ratio of the acetoacetal part and the butyl acetal part is in the range of 7:3 to 3:7, desirable adhesive strength can be achieved. It was discovered that solder heat resistance can be obtained, and the present invention was completed.

In other words, the present invention does not merely adjust the degree of polymerization, but also provides a mixed acetal in which the weight ratio of the acetoacetal part and the butyl acetal part is adjusted within a certain range, which is superior by limiting the degree of acetalization to a certain range. The purpose of the present invention is to provide an adhesive containing polyvinyl acetal as a main component.

The polyvinyl acetal according to the present invention has a polymerization degree of 1500 to
25001 preferably 1800-2500.

If it is less than 1500, both adhesiveness and heat resistance are insufficient;
When it is 500 or more, the viscosity of the adhesive composition is high, and the practicality is poor, and the heat resistance does not increase much.

Polyvinyl acetal, which is the main component of the present invention, consists of a vinyl acetal portion x, a vinyl alcohol portion y, and a vinyl acetate portion z, as shown in the following formula.

The vinyl acetate portion of polyvinyl acetal is hydrolyzed using a strong alkaline solution, and the remaining alkali is back-titrated with an acid to determine the weight of the two portions in the total sample, i.e. -+. It was calculated as the weight percent of CH2-C:H-→0C0CH3Z.

The vinyl alcohol part is acetylated with a mixture of pyridine and acetic anhydride, and the unreacted acetic acid is added with alkali.
, the weight of +CH2-7H+
It was calculated as 3.

The weight of the vinyl acetal part []o% is [], = 100
Find it as −([], +[]2). Further, the weight ratio of the acetoacetal portion (a) to the butyl 5-acetal portion (b) was determined using an infrared spectrophotometer to be described later. In addition, the smaller the residual vinyl acetate portion, the better the thermal stability.
It is not more than 2 wt%, preferably not more than 2 wt%.

Therefore, if commercially available completely saponified polyvinyl alcohol is used as a raw material, polyvinyl acetal within a preferable range can be obtained. The polyvinyl acetal which is the main component of the present invention requires that the weight ratio of the acetoacetal part to the butyl acetal part is 3:7 to 7:3. Generally, polyvinyl butyral is the most commonly used polyvinyl acetal for adhesives, followed by polyvinyl formal. Although polyvinyl formal has better heat resistance than polyvinyl butyral, it is not soluble in general-purpose solvents, and acetoacetal has insufficient adhesiveness and solubility. Mixed acetals using butyraldehyde and acetaldehyde are superior to butyl acetals, but those with a high acetoacetal ratio have poor solvent solubility and a tendency to gel, making them impractical. Those with a high proportion of butyl acetal are insufficient in improving soldering heat resistance.
Regarding mixed acetalization of polyvinyl alcohol, it is experimentally known that the composition ratio of the acetal produced does not match the composition ratio of the raw material aldehyde, and the relationship between the charging ratio and the composition ratio of the acetal produced depends on factors such as solvent, reaction time, and reaction temperature. It is impossible to calculate the composition ratio based on the preparation ratio because of the significant influence.

Generally, when acetaldehyde and butyraldehyde are charged at the same time, acetoacetalization proceeds first, and then butyralization proceeds gradually and exchange with acetoacetal occurs.

In addition, only acetaldehyde is charged first, and after a sufficient reaction, the exchange with boule proceeds. Conversely, if butyraldehyde is charged first and acetaldehyde is added after sufficient reaction, acetoacetalization will proceed. In any case, these reactions will proceed gradually, and it will take 10 minutes to reach complete equilibrium. It is expected to take several hours. death,
Therefore, in order to make the ratio of the acetoacetal part and the butyl acetal part to 7:3 to 3:7 by weight, the preparation ratio should be determined by actually measuring with an infrared spectrophotometer or other measuring method, which will be described later. Determine reaction conditions such as reaction time, reaction temperature, preparation method, solvent, etc. When polyvinyl alcohol is acetalized, it is possible to use either a solvent method in an organic solvent such as alcohol or a water method in water.
The solvent method makes it easier to freely control the reaction ratio of acetaldehyde and butyraldehyde, and it is easier to obtain a homogeneous product.

In the aqueous method, acetal tends to precipitate or gel, so there is a limit to the ratio of amounts used in order to react in a homogeneous system. Incidentally, when the method of Example 1 of JP-A No. 55-27342 was repeated, the composition ratio of acetal produced was 80:20 even though the charging ratio of para-aldehyde to n-butyraldehyde was 53:78. It was hot. It is also possible to use polyvinyl acetate as a raw material and perform saponification and acetalization. It is not necessary to completely acetalize the vinyl alcohol groups; the remaining hydroxyl groups in the polyvinyl acetal react with the methylol groups in the thermosetting resin such as phenol resin that is blended into the adhesive composition and are cured, so the remaining vinyl alcohol portion If it is less than 14 wt%, there will be a shortage of hydroxyl groups, making it difficult to cure and reducing heat resistance.

Furthermore, if the residual vinyl alcohol portion exceeds 21 wt%, the solubility in organic solvents decreases, making it unusable. To produce an adhesive for printed circuit laminates using polyvinyl acetal, which is the main component of the present invention, a phenolic resin,
Known adhesive components such as amino resin, epoxy resin, isocyanate, and soluble polyurethane are selected and dissolved in a solvent. Solvents include ketones such as acetone and methyl ethyl ketone, alcohols such as methanol, ethanol, butanol, and aromatic hydrocarbons such as toluene and xylene. These solvents can be used as a mixed solvent depending on the processing conditions. There is. The phenolic resin is a soluble phenol/formalin resin, and the cresol type is more common than the novolak type.

Also included are modified phenolic resins. In addition, modified melamine resins such as melamine resin, urea resin, methylated melamine resin, and butylated melamine resin are also used as the amino resin. Examples of the epoxy resin include bisphenol type epoxy resins. Although there are no particular limitations on the other adhesive components and their blending ratio, desirable examples include the following.

or etc.

Note that an antioxidant and other additives may be appropriately blended as necessary.

The present invention will be specifically explained below with reference to Examples.

Example 1 Production of mixed acetal Add methanol 4009 to a glass flask equipped with a stirrer in 11.
, 35% hydrochloric acid 59 was added, and then completely saponified polyvinyl alcohol with a degree of polymerization of 1950 was added to 829 ml while stirring.
Added.

Next, 30 f11 of acetaldehyde and 289 g of butyraldehyde were added to this, and the mixture was reacted at a temperature of 60° C. for 6 hours. After the reaction was completed, it was cooled and neutralized by adding 209 g of a 10% aqueous solution of caustic soda.

This was precipitated with water, washed with water and dried.

The product was dissolved in a mixture of ethanol and toluene in a weight ratio of 1:1 to form a 5% solution. Its viscosity is 11 at 20℃
It was 7cps. Its composition is vinyl acetate 1
．． 5 wt%, vinyl alcohol 16 wt%, and the ratio of acetoacetal to butyl acetal in the mixed acetal was 50:50 by weight. The weight ratio of acetoacetal and butyl acetal in the mixed acetal was determined using an infrared spectrophotometer, and was determined by using an infrared spectrophotometer to calculate the weight ratio of 1,3 dioxane ring containing C3H7 to 1000? The characteristic absorption of 1,3 dioxane ring containing CH3-CH-CH
945 due to 2-CH-? It was calculated by the absorbance ratio of the characteristic absorption.

Adhesive production 70 parts of mixed polyvinyl acetal, 550 parts of a mixture of organic solvents methyl ethyl ketone, methanol, and toluene in equal weight ratios, and a phenol resin solution with a solid content of 60% (Gunei Chemical Industry product name "AP-106") ), 50 parts of methylolated melamine resin (Sumitomo Chemical Co., Ltd. Hexamethoxymethylmelamine trade name "Sumimar MlOOl2O part") with a solid content of 50% were mixed to prepare an adhesive.

Apply the adhesive obtained in this example to the matte side of the copper foil for 30 minutes.
~351/Trl (solid content equivalent) applied and 10% at 80℃
The adhesive-coated copper foil was prepared by drying at 150° C. for 5 minutes.

Place this on several sheets of phenol resin-impregnated paper and
~170℃, 130kg/? A copper-clad laminate was produced by heat-pressing for 1 hour under the following conditions, and its solder heat resistance and adhesiveness were evaluated, and the results are shown in Tables 1 to 3 as Example 11. Example 2 Same as Example 1 except that polyvinyl alcohol with various degrees of polymerization was used instead of polyvinyl alcohol with a degree of polymerization of 1950, the weight ratio of acetoacetal and butyl acetal was about 50:50, and the vinyl alcohol portion was about 16 wt%. ,
A mixed acetal with a vinyl acetate content of about 3 wt % or less was obtained, a copper-clad laminate was prepared, and the solder heat resistance and adhesive strength were measured.

The results are shown in Table 1 as Experimental Waterfalls 1 to 6. Example 3 A mixed acetal was produced in the same manner as in Example 1, except that the amounts of acetaldehyde and butyraldehyde were changed, and then a copper foil laminate was produced.

The mixed acetal has a polymerization degree of 19501, a weight ratio of acetoacetal and butyl acetal of 50:50, a vinyl acetate portion of 3 wt% or less, a charge amount of acetaldehyde and butyraldehyde, physical properties of the mixed acetal, soldering heat resistance of the copper-clad laminate, and The adhesive strength is shown in Table 2 as experimental results J-9. Example 4 A mixed polyvinyl acetal was prepared in the same manner as in Example 1, except that the amount of acetaldehyde charged and the amount of butyraldehyde charged were changed, and then a copper-clad laminate was manufactured.

The mixed acetal had a polymerization degree of 19501, a vinyl alcohol portion of about 16 wt%, and a vinyl acetate portion of 2 wt% or less. The physical properties of the mixed acetal and the solder heat resistance and adhesive strength of the copper-clad laminates are shown in Table 3 as Experiments 746.10 to 13. In addition, soldering heat resistance is determined according to JISC648L by the time until swelling occurs in a 260°C solder bath (S
ec) was measured.

Adhesive strength was measured according to JISC648l. Solution viscosity was measured for a 5% solution using ethanol, toluene, 1:1 solvent.

The melting point was measured using a differential calorimeter DS manufactured by PerkinElmer.
It was measured using C-1B type.

The state of the blend was determined by visually observing the state of dissolution of the blend at room temperature.

Claims (1)

[Claims] 1 Acetoacetal-butyl acetal mixed polyvinyl acetal with a degree of polymerization of 1500 to 2500, in which the weight ratio of the acetoacetal part to the butyl acetal part is 3:7 to 7:3, and the vinyl alcohol part is 14 to 21. An adhesive for printed circuit laminates whose main component is polyvinyl acetal having a vinyl acetate content of 3% by weight or less.