JPS61278519A - Purification of polymer having carboxylic groups on both ends - Google Patents

Abstract

PURPOSE:To decrease ionic impurities contained in a polymer without any loss of the polymer easily by dissolution, by contacting a polymer having carboxyl groups on both ends with water in the presence of a ketone which is a good solvent therefor and is miscible with water. CONSTITUTION:A polymer having carboxyl groups on both ends (e.g., 1,3- butadiene/acrylonitrile copolymer having carboxyl groups on both ends) and containing ionic impurities such as Na is contacted with water in the presence of a ketone (e.g., acetone) which is a good solvent therefor and is miscible with water. This mixture is settled or, desirably, centrifuged to separate a polymer solution layer from a water/solvent layer containing transferred ionic impurities. The solvent and the water are distilled from the polymer solution to obtain a polymer freed of ionic impurities. The obtained purified polymer can be suitably used as, e.g., a flexibility-inparting agent used in sealing a semiconductor with an epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to the purification of a double-terminated carboxyl polymer, which is a liquid polymer. Double-terminated carboxyl polymers have recently attracted attention as impact-resistance modifiers for epoxy resins and the like, and their usage has also increased significantly.

In particular, both terminal carboxyl 1,3-butadiene-
Acrylonitrile copolymers have good compatibility with epoxy resins, so they are used in large quantities in applications that require high performance.

On the other hand, in the electronics semiconductor industry field.

As the degree of integration of LSI increases, chip size increases, and wiring becomes finer, thermal stress generated between the epoxy resin used for semiconductor encapsulation and silicon elements causes cracks, which has become a problem. There is. It is known that a two-end carboxyl polymer is extremely effective as this stress reducing agent. In addition, in order to improve the moisture resistance of semiconductor encapsulation resins, the requirement to reduce ionic impurities such as Na is becoming increasingly strict. Therefore, it is essential to increase the purity of epoxy resins, and it is essential to improve the purity of epoxy resins. There is also a strong demand for high purity of terminal carboxyl polymers.Double-terminated carboxyl polymers with a functional group number of 1.85 to 2.01 in the polymer molecule use diazocyano acid as a radical polymerization initiator. NaCA is produced as a by-product during this diazocyano acid synthesis.Based on this NaC!t (30 to 300 ppm of Na remains in commercially available double-terminated carboxyl polymers), When used as a flexibility imparting agent for epoxy resins for semiconductor encapsulation, it adversely affects moisture resistance.The Na content of the polymer is desired to be 5 ppm or less.

[Conventional technology]

The following methods are known to remove residual %Nacz and purify the polymer.

(1) Dissolve the polymer in a good solvent and use NaC! t is removed as a precipitate.

(2) Wash the polymer directly with water.

(3) Dissolve the polymer in a good solvent and bring it into contact with water.

[Problems to be Solved by the Invention] However, in method (1), a large amount of solvent is required to lower the viscosity of the solution, and the effect of reducing Na(,t) is not large (Comparative Example 1, 2).The method (2) does not allow sufficient contact between the polymer and water, and it is difficult to separate the water trapped in the polymer.
The aC6 reduction effect is small. Case (3) 1 When aromatic hydrocarbons, etc., which are usually considered good solvents for polymers and are immiscible with water, are used.

When the polymer, solvent, and water come into contact, emulsification is severe and the polymer layer and the water layer are not clearly separated even when the polymer is left standing or centrifuged at over 10,000 G, and a cloudy layer is present at the interface. Recovering only one layer of polymer has the disadvantage of high polymer loss. Furthermore, if an ether solvent such as tetrahydrofuran, which is a good solvent for polymers, is used, the interface will be clear, but it will be expensive and there is a risk of explosion due to the formation of peroxide when heated, such as when drying siborimer.

[Means for solving problems]

The inventors completed this invention as a result of intensive research into a purification method that solves the above-mentioned drawbacks.

That is, the present invention relates to a purification method for reducing ionic impurities contained in a dipolymer.

@) After contacting the double-terminated carboxyl polymer with water in the presence of a ketone that is a good solvent and is miscible with water, it is left to stand, preferably centrifuged, and the bipolymer solution layer is separated from impurity-containing water. The present invention relates to a method for purifying a double-terminated carboxyl polymer, which comprises: - separating the polymer from the solvent layer; (b) distilling off the solvent and water from the polymer solution to obtain a purified polymer;

According to this invention, the Na content in the 9-polymer can be greatly reduced, and if necessary, by repeating the step @),
This purification reduced the concentration to below 1 ppm.

The polymer itself does not lose any of its characteristic properties, and the loss of the polymer during purification is small. As the double-terminated carboxyl polymer, a commercially available butadiene and acrylonitrile copolymer having an average molecular weight of 1,000 to 10,000, a butadiene homopolymer, sulfur cyanide, a keto acid, and hydrazine are reacted in an aqueous solution.

A hydrazo compound is obtained, which is oxidized by adding chlorine gas to produce azobiscyano acid, and then acetone is added to dissolve the produced azobiscyano acid, and most of the by-produced NaC4 is removed as an aqueous solution or crystals. Liquid polybutadiene with carboxyl terminals at both ends obtained by polymerizing butadiene or butadiene and acrylonitrile in an acetone solvent using an acetone-aqueous solution of as a polymerization initiator.

Alternatively, there may be mentioned a combined product obtained by distilling off most of the remaining monomers and solvent from a polymerization solution of a liquid butadiene-acrylonitrile copolymer having carboxyl terminals at both ends.

In the present invention, suitable ketones that are miscible with water and used as a good solvent include acetone and methyl ethyl ketone. In the case of acetone.

Ultrapure water, which is a very poor solvent for butadiene homopolymer, is used.

For contacting the polymer with water, the 9-polymer may be dissolved in a good solvent and then the water may be brought into contact with the 1-polymer.

It doesn't matter if they are brought into contact with water at the same time. After contact with water, the polymer solution layer and the water layer may be separated by standing still, but it is preferable to use a centrifuge. The time for separation of both layers is significantly reduced.

When the polymer is a butadiene-acrylonitrile copolymer and a solvent other than acetone is used, the amount of the good solvent for 100 parts by weight of the TL polymer is the amount of the polymer, good solvent, and water at its boiling point or at 100°C. The amount of solvent used is greater than or equal to the amount of solvent based on the inherent solubility of the solvent. The amount of water is 1 polymer
5 parts by weight or more of water is used per 00 parts by weight. just,! From the viewpoint of industrial benefits such as the solubility of coalescence and the efficiency of contact with water and the viscosity of the dipolymer-water contact liquid and productivity, the solvent is 30 to 300 parts by weight and the water is 50 parts by weight for 100 parts by weight of the dipolymer. ~300 parts by weight is preferred. When the good solvent is acetone, it is per 100 parts by weight of the polymer.

40 to 200 parts by weight, the amount of water is 920 to 200 parts by weight based on the amount of solvent used.
40 parts by weight is preferred. Outside this range, N
Will the degree of decrease in a content become smaller?

Reproducibility of Na content reduction is difficult to obtain.

When the polymer is a butadiene homopolymer, acetone cannot be used because it is a poor solvent for the polymer.

The amounts of the polymer, good solvent, and water are the same as in the case of the copolymer.

In the present invention, the polymer is used in the presence of a good solvent.

The temperature at which it is brought into contact with water is preferably 5 to 100°C.

The temperature for standing and centrifugation is 5°C to 1° below the boiling point of the solvent used.
Temperatures down to 0°C are preferred. Pressure is normal pressure.

Either under increased pressure or reduced pressure may be used.

For centrifugation, a common centrifuge used by those skilled in the art is used, preferably a cylindrical Sharpless type.

The evaporator for distilling off the solvent and water from the polymer solution is a horizontal centrifugal thin film evaporator, a vertical centrifugal thin film evaporator [Example] Example 1 A double-terminated carboxyl butadiene-acrylonitrile copolymer containing 31 ppm Na (Acrylonitrile content 1
7% by weight, average molecular weight 3500) 36.0 was placed in a 150t container equipped with a stirrer, and methyl ethyl ketone 36.
．． OKy was added and dissolved under stirring.

Pure water here14. aKq was added and brought into contact with the polymer solution under stirring. This liquid was pale yellow and slightly cloudy. This pale yellow cloudy liquid was sent to a cylindrical centrifuge with a rotational speed of 1500 rpm using a plunger pump at a supply rate of 30 t/hr. A pale yellow polymer methyl ethyl ketone solution flowed out from the light liquid side outlet of the centrifuge, and waste water containing a small amount of methyl ethyl ketone flowed out from the heavy liquid side outlet. 3
Continuous liquid feeding was performed for hours. Separation of heavy liquid and light liquid is good.

The outflow amount of heavy liquid and light liquid per unit time was also constant.

The light liquid side is a methyl ethyl ketone solution of the polymer.

The concentrate obtained by passing it through a horizontal centrifugal thin film evaporator once at 133°C and 100 Torr under a heating medium condition is evaporated once again.
By passing at 10 Torr under the heating medium condition of 06°C,
A dried product of the polymer was obtained. The Na content in this polymer was 0.6 ppm as a result of atomic absorption spectrometry.

Example 2 Both terminal carboxyl butadiene-acrylonitrile copolymer containing 31 ppm Na (acrylonitrile content 1
7%, average molecular weight 3500) was placed in a 100 t container equipped with a stirrer, and 30.0 kg of acetone was added thereto and dissolved under stirring. Pure water 9 and OK7 were added thereto, and the mixture was brought into contact with the polymer solution while stirring.

This liquid was pale yellow and cloudy. This pale yellow cloudy liquid was sent to a cylindrical centrifuge at a rotational speed f 5000 rpm using a plunger pump at a supply rate of 17.5 L/hr. A pale yellow acetone solution of polymer flowed out from the heavy liquid side outlet of the centrifuge, and acetone-mixed wastewater flowed out from the light liquid side outlet. Continuous liquid feeding was performed for 4 hours. Separation of heavy liquid and light liquid was good, and the amount of heavy liquid and light liquid per unit time was also constant. The acetone solution of the polymer on the heavy liquid side is sent to a horizontal centrifugal thin film evaporator, and passed through it once at 200 TOrr under a heating medium condition of 153°C.
A dry product of the copolymer was obtained by passing the mixture under a heating medium condition of 33°C and 10 Torr. The Na content in this polymer is
The result of atomic absorption spectrometry was 1.2 ppm.

Examples 3 to 5 1007 of each of the following three types of both-end carboxyl liquid polymers containing Na were placed in a 500 ml separating funnel.Next, 1002 of methyl ethyl ketone and 302 of water were added, and the mixture was heated in a camera at 20°C for 15 minutes. It was 0. The liquid was pale yellow and cloudy.

Transfer this viscous liquid to a centrifuge tube and centrifuge at 550° rpm at 20°C.
Centrifugation was performed for 15 minutes. There was a clear separation into a slightly opaque yellow upper layer consisting of a solution of the polymer in methyl ethyl ketone and a clear lower layer. The upper layer was transferred to an eggplant-shaped flask, and after distilling off the solvent, it was vacuum-dried at 80°C overnight. In both cases, polymer loss is small, and the Na content in the polymer is 1 p.
It was below pm.

The results are summarized in Table 1.

Examples 6 to 8 Both terminal carboxyl butadiene-acrylonitrile copolymer containing 31 ppm Na (acrylonitrile content 1
7chi, average molecular weight 3500) 100.01 to 500
．． / into a separating funnel, add 100y of acetone, and after dissolving, adjust the amount of water to 2°f, 30f, 40f.
and variable. Each was shaken for 15 minutes at 25°C on a shaker. The liquid was pale yellow and cloudy. This was transferred to a centrifuge tube and centrifuged at 20°C and 5500 rpm for 15 minutes. Both were clearly separated into an upper layer consisting of a transparent water-acetone layer and a lower layer consisting of a transparent polymer solution in acetone. Transfer the lower layer to an eggplant-shaped flask and evaporate the solvent.

- Vacuum drying at 80'C overnight. In all cases, polymer loss was small, and the Na content in the polymer was 1 ppm or less.

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Table 2 Comparative Examples 1 to 2 Double-terminated carboxyl butadiene-acrylonitrile copolymer containing 31 ppm Na (acrylonitrile content 1
7chi, average molecular weight 350G) 10f each 1002
After dissolving in 0 methyl ethyl ketone and toluene, the polymer solution was transferred to a centrifuge tube, filtered at 20"C, and centrifuged at 5500 rpm for 0 minutes. After this, the polymer solution was carefully collected, and after the solvent was distilled off, it was incubated at 80"C overnight. A polymer was obtained by vacuum drying.

The results are summarized in Table 3.

[1 Comparative Example 3 Water 1007 was added to the same polymer 1001iF used in Comparative Example 1, and the mixture was washed with stirring for 15 minutes under a high-speed water flow.
Centrifugation was performed for 15 minutes at 0°C with a centrifugal effect of 5000G, but the separation of the polymer and water was not good, and the amount of water recovered was only about 2Of. After drying the first layer of white polymer, the +Na content was measured. It was 23 ppm.

Comparative Example 4 The same polymer 100.02 used in Comparative Example 1 was
Pour into a 00ml separating funnel and add 1ill of toluene.
, Of, add water 302 and heat to 20°C1 with a shaker.
It was lively for 5 minutes. The liquid was pale yellow and strongly cloudy. Transfer this viscous liquid to a centrifuge tube and incubate at 20°C and 550°rpm for 6 hours.
Centrifuged for 0 minutes. This centrifugation did not result in separation into 92 layers, and a wide white tofu-like layer existed between the slightly opaque upper layer consisting of a toluene solution of pale yellow polymer and the transparent aqueous layer. After drying the toluene solution layer of the polymer, the weight was measured to be 97.01, and the polymer loss was 3%. Moreover, the Na content in the polymer was 3.2 ppm.

〔Effect of the invention〕

As mentioned above, according to the present invention, the properties of the dipolymer are not impaired;
The Na content in the polymer can be greatly reduced with simple operations and less loss of polymer due to purification.

Claims (1)

[Scope of Claims] In a purification method for reducing ionic impurities contained in a polymer, (a) a carboxyl-terminated polymer is purified with water in the presence of a ketone that is a good solvent and is miscible with water. After contacting with
(b) Distilling off the solvent and water from the polymer solution to obtain a purified polymer; A method for purifying a double-terminated carboxyl polymer.