JPH0362721B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to the purification of a double-terminated carboxyl-terminated 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 obtained by copolymerizing 1,3-butadiene and acrylonitrile
-Butadiene-acrylonitrile copolymer has good compatibility with epoxy resins, so it is used in large amounts in applications that require high performance. On the other hand, in the semiconductor industry of electronics, as the degree of integration of LSI increases, chip size increases, and wiring becomes finer, thermal stress occurs between the epoxy resin used for semiconductor encapsulation and silicon elements. As a result, cracks occur and become a problem. It is known that a double-terminated carboxyl polymer is extremely effective as this stress reducing agent. Also, to improve the moisture resistance of semiconductor encapsulation resin.
Requirements for reducing ionic impurities such as Na ⁺ are becoming increasingly strict. Therefore, it is essential to increase the purity of the epoxy resin, and there is also a strong demand for a highly purified double-terminated carboxyl polymer as a flexibility imparting agent. Number of functional groups per polymer molecule is 1.85
A double-terminated carboxyl-terminated polymer having a molecular weight of ~2.01 is produced using diazocyano acid as a radical polymerization initiator. NaCl is produced as a byproduct during this diazocyano acid synthesis. Commercially available double-terminated carboxyl polymers contain 30% Na based on this NaCl.
~300ppm remains, and when used as a flexibility imparting agent for epoxy resin for semiconductor encapsulation,
Adversely affects moisture resistance. The Na content of the polymer is
A level of 5ppm or less is desired. [Prior Art] The following methods are known for purifying polymers by removing residual NaCl. (1) Dissolve the polymer in a good solvent and remove NaCl 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, method (1) requires a large amount of solvent to lower the viscosity of the solution, and
The effect of reducing NaCl is not large (Comparative Examples 1 and 2).
In method (2), the effect of reducing NaCl is small because sufficient contact between the polymer and water is not carried out and it is difficult to separate the water entrapped in the polymer.
In the case of (3), when using aromatic hydrocarbons, which are usually thought to be good solvents for polymers and are immiscible with water, when the polymer, solvent, and water come into contact, emulsification is strong, not to mention when the polymer is allowed to stand still. Even if centrifugation is performed at over 10,000 G, the polymer layer and aqueous layer are not clearly separated, and a cloudy layer exists widely at the interface. Therefore, if only the polymer layer is recovered, there will be a large loss of polymer. Furthermore, if an ether solvent such as tetrahydrofuran, which is a good solvent for the polymer, is used, the interface will be clear, which is expensive, and there is also the risk of explosion due to the formation of peroxide when the polymer is heated during drying. [Means for Solving the Problems] The inventors have completed this invention as a result of intensive research into purification methods that solve the above-mentioned drawbacks. That is, the present invention provides a purification method for reducing ionic impurities contained in a polymer, in which (a) a carboxyl-terminated polymer is purified with water in the presence of a ketone that is a good solvent for the polymer and is miscible with water. A step of separating the polymer solution layer from the water-solvent layer containing impurities by leaving to stand and preferably centrifuging after contacting with the polymer; (b) distilling off the solvent and water from the polymer solution to obtain a purified polymer; The present invention relates to a method for purifying a double-terminated carboxyl polymer, the method comprising the steps of: obtaining the following. According to this invention, the Na content in the polymer can be significantly reduced, and if necessary, by repeating step (a), it can be reduced to 1 ppm or less, and by this purification,
The polymer itself does not lose any of its characteristic properties, and the loss of the polymer during purification is small. Commercially available double-terminated carboxyl polymers have an average molecular weight of 1000~
10000 butadiene and acrylonitrile copolymer,
Butadiene homopolymer, sodium cyanide, keto acid, and hydrazine are reacted in an aqueous solution to obtain a hydrazo compound, which is oxidized with chlorine gas to produce azobiscyanoic acid, and then acetone is added to produce azobiscyanoic acid. Dissolved and produced as a by-product
Both-end carboxyl liquid polybutadiene, or both-end carboxyl liquid polybutadiene obtained by polymerizing butadiene or butadiene and acrylonitrile in an acetone solvent using an acetone-aqueous solution of azobiscyano acid from which most of NaCl has been removed as an aqueous solution or crystals as a polymerization initiator. Examples include crude polymers obtained by distilling off most of the remaining monomers and solvents from the polymerization solution of butadiene-acrylonitrile copolymer. 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, since it is a poor solvent for butadiene homopolymers, it is preferably used for copolymers. The water used is ion-exchanged water, preferably ultrapure water with extremely low ionic impurities. The polymer may be brought into contact with water by dissolving the polymer in a good solvent and then contacting the water.
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 polymer, good solvent, and water should be determined based on the boiling point or the amount of the solvent at 100°C for 100 parts by weight of the polymer. An amount greater than the amount of solvent based on inherent solubility is used. The amount of water used is 5 parts by weight or more per 100 parts by weight of the polymer. However, from the viewpoint of industrial benefits such as the solubility of the polymer, the efficiency of contact with water, the viscosity of the polymer-water contact liquid, and the productivity,
For 100 parts by weight, the solvent is 30 to 300 parts by weight, and the water is 30 to 300 parts by weight.
300 parts by weight is preferred. When the good solvent is acetone, it is preferably 40 to 200 parts by weight per 100 parts by weight of the polymer, and the amount of water is preferably 20 to 40 parts by weight per amount of the solvent used. If it deviates from this range, the degree of decrease in Na content will be small, or it will be difficult to obtain reproducibility of Na content decrease. 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 treated 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 preferably 5°C to 10°C lower than the boiling point of the solvent used. Pressure is normal pressure,
Either under increased pressure or reduced pressure may be used. For centrifugation, a common centrifugal separator used by those skilled in the art is used, but preferably a cylindrical shear press type is used. As the evaporator for distilling off the solvent and water from the polymer solution, centrifugal thin film evaporators such as a horizontal centrifugal thin film evaporator, a vertical centrifugal thin film evaporator, and a VL centrifugal thin film evaporator can be used. The purified polymer is obtained from the polymer solution by evaporation methods known per se. [Example] Example 1 36.0 kg of a double-terminated carboxyl butadiene-acrylonitrile copolymer containing 31 ppm Na (acrylonitrile content 17% by weight, average molecular weight 3500) was placed in a 150 container equipped with a stirrer, and 36.0 kg of methyl ethyl ketone was added. It was dissolved under stirring. pure water here
14.4Kg 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 rotation speed of 15,000 rpm using a plunger pump at a supply rate of 30/hr. A light yellow solution of polymer in methyl ethyl ketone flowed out from the light liquid side outlet of the centrifuge, and wastewater containing a small amount of methyl ethyl ketone flowed out from the heavy liquid side outlet. Continuous liquid feeding was carried out for 3 hours. Separation of heavy liquid and light liquid was good, and the outflow amount of heavy liquid and light liquid per unit time was also constant. The methyl ethyl ketone solution of the polymer on the light liquid side is sent to a horizontal centrifugal thin film evaporator, and passed through once at 100 Torr under a heating medium condition of 133°C.The obtained concentrate is then passed again under a heating medium condition of 133°C.
A dry product of the polymer was obtained by passing it through at 10 Torr. The Na content in this polymer was 0.6 ppm as a result of atomic absorption spectrometry. Example 2 30.0 kg of a double-terminated carboxyl butadiene-acrylonitrile copolymer containing 31 ppm Na (acrylonitrile content 17%, average molecular weight 3500) was placed in a 100-liter container equipped with a stirrer, and 30.0 kg of acetone was added thereto and dissolved under stirring. 9.0 kg of pure water was 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 is supplied with a plunger pump at a rotation speed of 17.5/hr.
The liquid was sent to a cylindrical centrifuge at 15,000 rpm. 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 the concentrate obtained by passing it through once at 200 Torr under a heating medium condition of 133°C is heated again at 10 Torr under a heating medium condition of 133°C.
A dry product of the polymer was obtained by passing the polymer through the filtrate. The Na content in this polymer was determined by atomic absorption spectrometry.
It was 1.2ppm. Examples 3 to 5 100 g of each of the following three types of liquid polymers with carboxyl ends containing Na were placed in a 500 ml separating funnel, and then 100 g of methyl ethyl ketone and 30 g of water were added.
g was added, and the mixture was shaken at 20°C for 15 minutes using a shaker. The liquid was pale yellow and cloudy. Transfer this viscous liquid to a centrifuge tube and spin at 5500 rpm at 20°C.
Centrifugation was performed for 15 minutes. There was a clear separation between a slightly opaque yellow polymer solution in methyl ethyl ketone upper layer and a clear lower layer. The upper layer was transferred to an eggplant-shaped flask, and after the solvent was distilled off, it was vacuum-dried at 80°C overnight. In all cases, polymer loss was small, and the Na content in the polymer was 1 ppm or less. The results are summarized in Table 1.

[Table] Examples 6 to 8 100.0 g of a double-terminated carboxyl butadiene-acrylonitrile copolymer containing 31 ppm Na (acrylonitrile content 17%, average molecular weight 3500) was placed in a 500 ml separating funnel, and then 100 g of acetone was added.
After dissolution, the amount of water added was varied to 20 g, 30 g, and 40 g. Each was shaken at 25°C for 15 minutes 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 acetone solution of the polymer. The lower layer was transferred to an eggplant-shaped flask, and the solvent was distilled off, followed by vacuum drying at 80°C overnight. In both cases, the loss of polymer is small, and the Na content in the polymer is also low.
It was less than 1 ppm. The purified polymers obtained in Examples 1 to 8 all showed good results as stress reducing agents when used in epoxy resins.

[Table] Comparative Examples 1 to 2 10 g of a double-terminated carboxyl butadiene-acrylonitrile copolymer containing 31 ppm Na (acrylonitrile content 17%, average molecular weight 3500)
After dissolving in 100 g of methyl ethyl ketone and toluene, it was transferred to a centrifuge tube and centrifuged at 5500 rpm for 30 minutes at 20°C. Thereafter, the polymer solution was carefully collected, and after the solvent was distilled off, it was vacuum dried at 80°C overnight to obtain a polymer. The results are summarized in Table 3.

〔Effect of the invention〕

As described above, according to the present invention, the Na content in the polymer can be significantly reduced without impairing the properties of the polymer, with simple operations and with little polymer loss due to purification.

Claims (1)

[Claims] 1. In a purification method for reducing ionic impurities contained in a polymer, (a) a double-terminated carboxyl polymer is treated in the presence of a ketone that is a good solvent for the polymer and is miscible with water. After contacting with water, the polymer solution layer is separated from the water-solvent layer containing impurities by leaving it still and preferably centrifuging; (b) distilling off the solvent and water from the polymer solution to purify the polymer solution; A method for purifying a double-terminated carboxyl polymer, comprising: a step of obtaining a polymer.