GB2030573A

GB2030573A - Hydrophilic polymer and process for producing the same

Info

Publication number: GB2030573A
Application number: GB7836829A
Authority: GB
Original assignee: Dainichiseika Color and Chemicals Mfg Co Ltd
Current assignee: Dainichiseika Color and Chemicals Mfg Co Ltd
Priority date: 1978-09-14
Filing date: 1978-09-14
Publication date: 1980-04-10
Also published as: GB2030573B

Abstract

A hydrophilic polymer comprising a main component of a block copolymer and/or a graft copolymer which has at least one hydrophobic hard segment-hydrophilic segment-hydrophobic hard segment unit wherein said hydrophilic segment has a hydrophilic group connected to a thioether bond on a side chain, may be produced by adding a thioalcohol group-containing compound, e.g. thioglycol orthioglycolic acid, to an unsaturated group of a block copolymer and/or a graft copolymer having at least one unit of hydrophobic hard segment-unsaturated segment-hydrophobic hard segment structure and, if necessary, modifying the terminal thio-alcohol-containing group to render it hydrophilic, e.g. by esterification. Typical starting polymers are polystyrene/polybutadiene/polystyrene, polyethyleneterephthalate- polyethylenemaleate- polyethyleneterephthalate and polyurethane-polyethylenemaleate- polyurethane block copolymers.

Description

SPECIFICATION Hydrophilic polymer and process for producing the same The present invention relates to a hydrophilic polymer comprising a main component of a block copolymer and/or a graft copolymer having special binding system of a hydrophobic hard segment and a hydrophilic segment having a hydrophilic group connected to thioether bond on a side chain, and to a process for producing the same. More particularly, it relates to novel hydrophilic polymers which have excellent water swelling and water absorbing properties and are useful as water repellents, water retainers, antistatic agents, perspiration absorbers or antidewers.

The conventional water insoluble hydrophilic polymers such as water swellable polymers and water absorbing polymers include (1) water insoluble polymers produced by modifying polyethylene-glycol (PEG), (2) polymers produced by crosslinking water sol uble hydrophilic random copolymers or homopolymers by various methods with sigma bonds to make them water insoluble and if necessary, further chelating the water insoluble polymers, and (3) polymers produced by grafting acrylonitrile on starch and, if necessary, further hydrolyzing the graft copolymer.

These hydrophilic polymers are useful as antiwater-leakage polymers, water retainers, antidewers, antistatic agents, cement reinforcing agents and perspiration absorbers.

These hydrophilic polymers have been studied for various purposes. There has not until now been produced a hydrophilic polymer having high water swelling degree and water swelling force and high gel stability in storage which can be controlled as desired.

The polymers (1) (modified PEG) have high water swelling degree but have low water swelling force which is further remarkably decreased by the addition of a material having high cohesive force.

Accordingly, the desired purpose could not be attained.

In the polymers (2), the water swelling degree is dependent upon the content of hydrophilic groups and the crosslinking degree which are mutually contradictory. The crosslinkage is formed by a chemically stable sigma bond, whereby it is not easy to treat the polymer in a post-treatmentortodisperse it in a medium.

The polymer (3) of acrylonitrile grafted starch, which may be hydrolyzed, one having high water absorption for absorbing 50 times of water to polymer, but the polymers are perishable in storage resulting in decomposition of the structure.

The present invention provides a hydrophilic polymer which comprises a main component of a block copolymer and/or a graft copolymer which has at least one unit of hydrophobic hard segmenthydrophilic segment-hydrophobic hard segment structure wherein said hydrophobic hard segment is a binding phase segment having an average molecular weight of more than 1,000 and said hydrophilic segment is a segment having a hydrophilic group connected to a thioether bond on a side chain and having an average molecular weight of more than 1,000.

The invention also provides a process for producing such a polymer which comprises adding a thioalcohol group-containing compound to an unsaturated group of block copolymer and/or a graft copolymer having a main component of at least one unit of hydrophobic hard segment-unsaturated segment-hydrophobic hard segment structure and, if necessary, modifying the terminal thio alcoholcontaining group to render it hydrophilic and form a hydrophilic segment having a hydrophilic group connected to a thioether bond on a side chain and having an average molecular weight of more than 1,000 and a hydrophobic hard segement having an average molecular weight of more than 1,000.

In this way there can be provided a water insoluble hydrophilic polymer having a suitable balanced water swelling degree and water swelling force, which is not perishable and can be post-treated or dispersed.

The block copolymer and/or a graft copolymer preferably has an average molecular weight of approximately 2,000.

The binding phase hydrophobic hard segments include polystyrene type, poly-a-methylstyrene type, polyethylene type, polypropylene type, polyurethane bond type polymers, aromatic ring containing polyester type polymers such as polyethyleneterephthal ate and polyamide bond type.

The hydrophilic segments are preferably formed by reacting a thioalcohol group containing compound with an unsaturated group of an cr, P-ethylene type segment such as polybutadiene, polychloroprene, polyisoprene and unsaturated polyester, modifying it if necessary and forming a hydrophilic group.

The block copolymer or the graft copolymer or mixture thereof has a specific binding system wherein at least two points of the unsaturated segment are bonded to the hydrophobic hard segments as a main component of the polymer (telechelictype, multi-type or radial type). It can contain a single type of hydrophobic hard segment-unsaturated segment The hydrophilic segment having a thioether bond in a side chain is produced by reacting a polymer or an oligomer having an a, p-ethylene type unsaturated bond with a thioalcohol group-containing compound, if necessary modifying it, and forming a hydrophilic group.

The average molecular weight of each of the hydrophobic bond segment and the unsaturated segment is higher than 1,000, preferably higher than 3,000.

The ratio of the hydrophobic hard segment in the polymer is generally in a range of about 5 to 95% preferably about 10 to 80%.

The thioalcohol group containing compound used in the preparation of the hydrophilic segment has hydrophilic property or is modified to the derivative having hydrophilic property.

Suitable thioalcohol group containing compounds include thioglycolic acid, thiohydroacrylic acid, thiolactic acid, thiomalic acid, thioethanolamine, p-diethylaminoethyl mercaptane, p-diethylaminoethyl mercaptane, pdiethylaminoprnpyl mercaptane, p-nitrnethyl mercaptane, thioglycol, thiophenol, thiocresol, thiosalicyclic acid etc. The thioalcohol group containing compounds having a terminal carboxylic group include the derivatives of metal salts, ammonium salts, organic amine salts, esters, urethanes and amides of the carboxylic acids.

The metal salts can have metals in groups I, II, or III of the periodic table and especially alkali metals.

The organic amine salts include primary, secondary and tertiary amines, alkanol amines and morpholine.

The thioalcohol group containing compounds further include the compound produced by reacting the terminal carboxylic group with isethionic acid, sarcosine, aminomethanic acid, taurine, N-methyltaurine, polyoxyethylene alkyl ether, polyoxyethylamine, N,N'-dialkyl ethanolamine (C1-C4), polyethyleneglycol etc.

The terminal amino group of the thioalcohol group containing compound can be modified to mineral acid salts, organic acid salts, amide bonds, secondary, tertiary and quaternary amine salts. The mineral acids include hydrochloric acid, phosphoric acid, sulfuric acid etc. The organic acids include formic acid, acetic acid, butyric acid, lactic acid, palmitic acid, oleic acid, stearic acid etc.

The thioalcohol group containing compounds further include derivatives of isethionates, oxycarboxylic acids and salts thereof, oxysulfonic acids and salts thereof, alkyl halides such as methyl chloride, acid anhydrides such as phthalic anhydride succinic anhydride maleic anhydride and salts, ethylenechlorohydrine and ethyleneoxide.

The thioalcohol group containing compounds having terminal alcoholic hydroxyl group include sulfates, nitrates and phosphates, thereof, and derivatives of acid anhydrides such as phthalic anhydride, succinic anhydride and maleic anhydride, and salts thereof, a-sulfofatty acids such as a-sulfostearic acid, er-sulfoparmitic acid and salts and esters thereof.

The process for an addition of the thioalcohol group containing compound to the unsaturated group of the a,p-ethylene type segment, can be the conventional addition reactions. Sometimes, the addition reactions for the unsaturated group can be completed without any catalyst depending upon high activity of the unsaturated group. However, in general, it is preferableto use a radical initiator such as azobis isobutyronitrile, azobiscyanovaleic acid, benzoylperoxide, lauroylperoxide, cumene hyd roperoxide, methyl ethyl ketone peroxide, ammonium persulfate, and alkali metal persulfate, hydrogen peroxide etc.

The amount of the initiator is in a range of 0.1 to 10 wt.% preferably 0.5 to 5 wt.% to the reactive polymer.

The solvents used in the reaction are dependent upon the kinds of the block copolymer and/or the graft copolymer.

Suitable solvents include hydrocarbon type solvents such as cyclohexane, toluene, xylol, terpene, pentane, naphthene; ether type solvents such as ethyleneglycol diethyl, methyl or ethyl ethers, (diethyl cellosolve, methyl cellosolve, ethyl cellosolve) dioxane; hydrophilic solvents such as water, methanol, ethanol, isopropanol, buthanol; and chlorine type solvents such as chloroform, carbon tetrachloride or mixture thereof.

The concentration in the reaction is usually in a range of 25 to 50 wt.% preferably 5 to 20 wt.%.

The molar ratio ofthethioalcohol group containing compound to the unsaturated group of the a,ss-ethylene type segement is in a range of 5 to 100 moleo/o, preferably 20 to 100 mole%.

The reaction temperature is usually in a range of 20 to 1 50 C, preferably 50 to 1 00 C.

The reaction atmosphere is preferably in an inert gas flow without air or in refluxing condition at the boiling point.

The reaction time is usually in a range of 0.5 to 10 hours preferably 3 to 5 hours. After the reaction, it is possible to use it in a form of solution. However, it is usual that the object compound is obtained by removing the solvent and purifying the compound.

The resulting hydrophilic polymers impart the special characteristics in comparison with the hydrophilic polymers obtained from the conventional random copolymers. For example, even though a hydrophilic group for water soluble is introduced, the polymer is not water soluble but the water swelling degree is about 50 times to the weight of the polymer.

The water swelling degree can be controlled as desired in a range of several times to about 50 times depending upon the kind and ratio of the hydrophilic group.

The polymers can be anionic, cationic, nonionic or amphoteric polymers.

In accordance with the present invention, hydrophilic polymers having specific characteristics suitable for the usages and uses can be provided.

The effects of the present invention can be attained by binding the hydrophilic segment for dissolving into water, with hydrophobic hard segments to prevent the solubilization into water.

The limitation of the introduction of the hydrophilic group can be the limitation of the break of the binding phase whereby the water swelling degree can be controlled depending upon the introduction of the hydrophilic group. As the result, even though the hydrophilic property of the polymer of the invention is significantly increased in comparison with that of the random polymer, the polymer of the invention is not dissolved into water whereby the range of the water swelling degree can be remarkably high.

Moreover, the swollen gel of the present invention is not decomposed by micro-organisms because it is not a modified natural material whereby the swollen gel can be stored for a long time. Moreover, the binding phase is not a crosslinkage in sigma bond whereby it can be opened by a solvent or heat.

The present invention will be further illustrated by certain examples. In the examples, the words of part and% mean part or% by weight.

EXAMPLE 1: In a reactor, 15 parts of a block copolymer of a main component of polystyrene - polybutadiene polystyrene having a polystyrene content of about 40 wt.%, and 185 parts of cyclohexane were charged and the block copolymer was dissolved by heating the mixture to the boiling point of cyclohexane, and the mixture was cooled to several C after purging, and then, 0.15 part of azobisisobutyronitrile was added and the mixture was heated again and 18 parts of thioglycolic acid was added dropwise during 10 to 15 minutes at the boiling point and the reaction was continued for about 5 hours at the boiling point.

As the result, the reaction mixture having milky and fluorescent color was obtained. The reaction mixture was cooled to 35 to 40"C and 80 parts of methanol containing 10% NaOH was added dropwise and the reaction mixture was poured into 1500 parts of methanol and the precipitate was washed with methanol and filtered and dried to obtain about 28 parts of the white reaction product. The reaction product was pulverized to obtain powdery hydrophilic polymer.

The reaction product was analyzed by IR spectrum. Figure 1 shows IR spectrum of the polymer as a starting material and Figure 2 shows IR spectrum of the product having free carboxylic acid group (the sodium salt was converted to the acid form).

In IR spectrum of the product of Figure 2, the absorption of

was found at 1700 cm~' but the absorptions of the double bond (-C=C-) of the polybutadiene segment at 970 to 980 cm-1 and 920 cm-' were not found in Figure 2. Accordingly, it is clearthatthe addition of thioglycolic acid to the double bond is attained.

The reaction product (sodium salt) was dipped in a distilled water to test the water swelling degree and it was found that the reaction product was swollen to about 40 to 45 times.

In the test of the water swelling degree, about 0.1 g of the sample was weighed (WO) and dipped in 100 ml of a distilled water for 24 hours and water remained on the surface was wiped off with a filter paper and the swollen sample was weighed (W) and the water swelling degree was given as (W/WO).

EXAMPLE 2: In a reactor, 15 parts of a block copolymer having a main component oftelechelictype polystyrenepolyisoprene-polystyrene having a polystyrene content of about 20 wt.% and 185 parts of cyclohexane were charged. In accordance with the process of Example 1,0.15 part of lauroyl peroxide and 19.5 parts of thioglycolic acid were added dropwise to perform the reaction and 85 parts of methanol containing 10% NaOH was added dropwise and the reaction product was precipitated in methanol and washed with methanol and filtered and dried to obtain about 19 parts of the reaction product. The reaction product was pulverized in powdery form.

The water swelling degree of the reaction product was about 50 times.

EXAMPLE 3: In the cyclohexane solution obtained by the reaction of Example 1, 35 parts oftriethanol amine was added and the mixture was refluxed until distilling off 3.5 parts of water. The reaction mixture was poured into 1000 parts of water and cyclohexane was evaporated under heating and stirring whereby the polymer was precipitated. The precipitate was cooled and filtered and dried at 35 to 40"C under a reduced pressure to obtain 50 parts of the reaction product.

The water swelling degree of the acetic acid salt of the reaction productwas about 10 times.

EXAMPLE4: In a reactor, 15 parts of a block copolymer having a main component of telechelic type polystyrenepolybutadiene-polystyrene having a polystyrene content of about 30 wt.% and 100 parts of toluene and 100 parts of cyclohexane were charged. In accordance with the process of Example 1, 0.15 part of azobisisobutyronitrile and 12.1 parts of thioglycol were added dropwise and the reaction was performed and the solvent was removed from the reaction mixture to obtain the reaction product. The water swelling degree of the product was about 2 times.

The reaction product was modified by a sulfuric acid esterification, an acylation or an esterification with sulfuric acid, succinic anhydride or oe-sulfopalmitic acid. The products and salts thereof had excellent water swelling degree.

EXAMPLE 5: In a reactor, 15 parts of a block copolymer having a main component of telechelic type polyethyleneterephthalate - polyethylene - maleate polyethyleneterephthalate having a polyethylene maleate content of about 70 wt.% obtained by condensing polyethyleneterephthalate having two terminal alcoholic hydroxyl groups with polyethylenemaleate having two terminal carboxyl groups and 100 parts oftoluene and 85 parts of dioxane were charged and the mixture was heated to the boiling point and it was purged with nitrogen and the mixture was heated to 1000C and 0.075 part of azobisisobutyronitrile was added and 7 parts of thioglycolic acid was added dropwise and the reaction was performed at 10000 for 3 hours. The reaction mixture was cooled to 400C and 30 times of methanol containing 10% NaOH was added dropwise and the mixture was stirred for 2 hours and poured into a large amount of methanol and it was kept in one day and the precipitate was washed with methanol and filtered and dried to obtain 20 parts of the reaction product. The water swelling degree of the product was about 5 times.

EXAMPLE 6: In a reactor, 15 parts of a block copolymer having a main component of telechelic type polyurethane polyethylenemaleate- polyurethane having a polyethylene maleate content of about 80 wt.% obtained by reacting polyurethane having two terminal isocyanate groups obtained from 4,4'diphenylmethane diisocyanate and ethyleneglycol with polyethylene maleate having two terminal alcoholic hydroxyl groups and 0.1 part of lauroyl peroxide, 100 parts of tetrahydrofuran and 50 parts of toluene were charged and the mixture was heated to 60 C in nitrogen gas flow and 7.8 parts of thioglycolic acid was added dropwise and the reaction was continued for 5 hours and the reaction mixture was cooled to 35 C and 34 parts of methanol having 10% NaOH was added dropwise and the mixture was stirred for 1 hour and the reaction mixture was poured into a large amount of methanol to precipitate the reaction product. The product was washed with methanol and filtered and dried to obtain about 19 parts of the product. The water swelling degree of the product was about 10 times.

EXAMPLE 7: A block copolymer having a main component of telechelic type polystyrene - polybutadiene - polystyrene (polystyrene content of 40%) was dissolved in cyclohexane and the addition of thioglycolic acid to the unsaturated double bond of the polymer was performed in the solution and then, the product was neutralized with a mixture of potassium t-butoxide containing methanol-methylethyl ketone-t-butanol (3:8:1) to obtain a dispersion of fine hydrophilic polymer (potassium salt of carboxylic acid : solid content of 14%).

EXAMPLE 8: A block copolymer having a main component of telechelic type polystyrene - polyisoprene - polystyrene (polystyrene content of 40 /O) was dissolved in cyclohexane and the addition of thioglycolic acid to the unsaturated double bond of the polymer was performed in the solution and then, toluene (0.3 times of cyclohexane) was added and the product was neutralized with a mixture of sodium hydroxide-methanol-methyl ethyl ketone-dioxane (1:1:1) to to obtain a dispersion of fine hydrophilic polymer having sodium salt of carboxylic acid (solid content of 21.5%).

EXAMPLE 9: In accordance with the process of Example 5, except using 21 wt. parts of a block copolymer having a main component of multi-type [(polyethyleneterephthalate)(polyethylenemale- ate)]n(polyethyleneterephthalate (n=2 to 4) having a polyethylenemaleate content of about 50 wt.% obtained by condensing polyethyleneterephthalate having two terminal alcoholic hydroxyl groups with polyethylenemaleate having two terminal carboxylic groups, an addition of thioglycolic acid to the block copolymer was performed with azobisisolbutyronitrile in a mixed solvent of toluene and dioxane and then, the reaction mixture was neutralized with a methanol solution of NaOH and the product was precipitated from methanol and then, it was filtered, washed and dried to obtain 25 wt. parts of the reaction product. The water swelling degree of the product was about2 times.

EXAMPLE 10: In accordance with the process of Example 2, except using 24 wt. parts of a graft copolymer of natural rubber-polystyrene having a polystyrene content of about 50 wt.% obtained by graft polymerizing styrene onto kneaded natural rubber with benzoylperoxide, an addition of thioglycolic acid to the graft copolymer was performed with lauroyl peroxide in a mixed solvent of cyclohexane and toluene (50:50) and then, the reaction mixture was neutralized with a methanol solution of NaOH and the product was precipitated from ethanol and then, it was filtered, washed and dried to obtain 35 wt. parts of the reaction product and the product was pulverized. The water swelling degree of the product was about 20 times.

EXAMPLE 11: Powdery polymer of Example 1 ..............1.5 1.5 parts Block copolymer of telechelic type 4 parts polystyrene-polybutadiene-polystyrene (polystyrene content of 40 wt.%) Naphthene type processing oil ...............6 6 parts The mixture of the components was heat-melted at 160 to 1700C and molded in a form of tape. The product was adhered on the segment for a shie!d processing whereby excellent water leakage resistance was attained.

The powdery hydrophilic polymer was blended and kneaded with each of natural rubber, isoprene rubber, nitrile rubber, ethylene-propylene-rubber or butyl rubber at ratio of 50:50 on a roll mill at40to 80 C to obtain each master batch of the rubber composition.

The mixture was diluted with each rubber to 2.5 times on the roll mill to obtain a sheet containing the hydrophilic polymer and the rubber at a ratio of 20:80 by weight. A piece was sampled from the sheet and the master batch and the piece was dipped into a distilled water for 2 days and the water swelling degree was measured. The results are as follows.

Diluted Master Diluted Master Kind of rubber product batch Natural rubber 9.2 times 17.7 times Isoprene rubber 9.9 times 39.6 times Nitrile rubber 9.4 times 24.9 times Ethylenepropylene rubber 7.5 times 17.6 times Butyl rubber 8.8 times 28.3 times These compositions were useful as a caulking compound and a sealant with the other additives.

EXAMPLE 12: The product of Example 2 was blended and kneaded with butyl rubber. Excellent water leakage resistance was found and the composition was useful as a sealing composition.

When the product of Example 10 was used, excellent water leakage resistance was imparted.

EXAMPLE 13: The product of Example 3 was blended and kneaded with polyethylene to obtain a composition having excellent antistatic property.

When the product of Example 9 was used, excel lent antistatic property was imparted.

EXAMPLE 14: The product of Example 4 had excellent adhesive property to glass and had antifogging effect.

EXAMPLE 15: The product of Example 5 was added to polyester fiber to obtain a composition having excellent antistatic effect.

EXAMPLE 16: The product of Example 6 was added to a leather to obtain effects of air permeability and perspiration absorbability.

EXAMPLE 17: The dispersion of the fine hydrophilic polymer of Example 7 was admixed with a toluene solution containing 15% styrene-butadiene rubber (styrene content of 23.5%) to obtain paint type hydrophilic polymer compositions.

Content of hydrophilic polymer 50"/0 20% in dried sheet 14% dispersion of fine hydrophilic polymer 51.7 parts 21.1 parts 15% toluene solution of styrene-butadiene rubber 48.3 parts 78.9 parts Total 100 parts 100 parts The paint composition was coated on a parting sheet (peeling) and dried in air for one night and predried at 70"C and dried at 1 000C for 2 hours to obtain a water swellable styrene-butadiene rubber type film.

A piece (8x2 cm) was sampled from the film and the water swelling degree was measured. The results are as follows.

Water swelling Water swelling Weight degree after degree after Sample film of film 30 minutes 1 hour Film containing 50% of hydrophilic 0.162 g 8.8 times 14.5 times polymer Film containing 20% of hydrophilic 0.213 9 4.1 times 5.5 times polymer A tricot cotton fabric was disposed on a parting paper (peeling) and a dispersion of the hydrophilic polymer and the styrene-butadiene rubber (20:80) (a fabric treating agent type) was immersed in the tricot cotton fabric and dried in air and predried at 600C and dried at 80"C for 3 hours.The weight ratio of the fabric to the polymers in the dried product was 1:1.5.

A piece was sampled from the product and dipped into a distilled water to swell it. The rough tricot fabric was completely clogged by the swollen polymers.

The water swelling degree of the hydrophilic polymer was about 4 times.

The hydrophilic polymer treated fabric was used as a packing material or a sealing material at each joint in a building a pipe for water supply and a tent, whereby the water leakage resistant effect by the water absorption to increase a thickness was attained to be remarkably useful.

EXAMPLE 18: The dispersion of fine hydrophilic polymer of Example 8 was prepared.

A rubber solution having a solid content of 15% was prepared by dissolving 7.5 parts of styrenebutadiene rubber (styrene content of 23.5%) and 7.5 parts of styrene-butadiene type thermoplastic resin (styrene content of 40 /O) in 85 parts of toluene.

A paint type hydrophilic polymer composition was prepared by uniformly mixing 15 parts of the dispersion of the hydrophilic polymer and 85 parts of the toluene solution of the rubber under stirring.

The composition was coated on a parting paper and dried to obtain the rubber sheet containing the hydrophilic polymer. The water swelling degree of the sheet was 4 times.

The paint type hydrophilic polymer composition was coated on an agricultural polyvinyl chloride film and dried to obtain a hydrophilic polymer coated film having thickness of coated layer of 100 ju. A green house for accelerating and protecting germination and growth of the plants was prepared by using the coated film. The dews caused by tempera ture difference were not adhered on an inner surface of the coated film to prevent dews. Even though the coated layer absorbed water, the dry feeling was attained.

In the same manner, when the paint type hyd rophilic polymer composition was coated on a sur face of a wall or a ceiling in a house especially in a bath room, the formation of dews was prevented.

A paint type hydrophilic polymer composition was prepared in accordance with the same manner except using a solution of 15% of carboxylated vinyl chloride-vinyl acetate resin, and dibutyl phthalate (80:20) in a mixed solvent of methyl ethyl ketone and toluene (50:50) instead of the toluene solution of the rubber and adding a stabilizer for vinyl chloride.

The paint type hydrophilic polymer composition was coated on the film, the wall and the ceiling whereby the same effect for preventing the formation of dews was effectively attained.

Figure 1 is IR spectrum of the styrene-butadiene block copolymer used as the starting material in Example 1 and Figure 2 is IR spectrum of the hydrophilic polymer obtained in Example 1.

Claims

1. A hydrophilic polymer which comprises a main component of a block copolymer and/or a graft copolymer which has at least one unit of hydrophobic hard segment-hydrophilic segmenthydrophobic hard segment structure wherein said hydrophobic hard segment is a binding phase segment having an average molecular weight of more than 1,000 and said hydrophilic segment is a segment having a hydrophilic group connected to a thioether bond on a side chain and having an average molecular weight of more than 1,000.

2. A hydrophilic polymer according to claim 1 which comprises a main component of polystyrene-hydrophilic segment-polystyrene, polyethyleneterephthalate-hydroph ilic segmentpolyethyleneterephthalate or polyurethanehydrophilic segment-polyurethane, wherein said hydrophilic segment is the product of an addition reaction ofathioalcohol group-containing compound to an unsaturated double bond of an a, ss-ethylenic component.

3. A hydrophilic polymer according to claim 1 or claim 2 wherein the block copolymer and/or graft copolymer has an average molecular wt. approximately 2,000.

4. A hydrophilic polymer according to any preceding claim wherein the average molecular weight of the hydrophobic bond segment and of the unsaturated bond segment are higher than 3,000.

5. A hydrophilic polymer according to claim 1 substantially as herein described with reference to the Examples.

6. A process for producing a hydrophilic polymer which comprises adding a thioalcohol groupcontaining compound to an unsaturated group of a block copolymer and/or a graft copolymer having a main component of at least one unit of hydrophobic hard segment-unsaturated segment-hydrophobic hard segment structure and, if necessary, modifying the terminal thio-alcohol-containing group to render it hydrophilic and form a hydrophilic segment hav ing a hydrophilic group connected to a thioether bond on a side chain and having an average molecu lar weight of more than 1,000 and a hydrophobic hard segment having an average molecular weight of more than 1,000.

7. A process according to claim 6 wherein the thioalcohol group-containing compound is a compound having a thioether bond and a hydrophilic terminal group which is a carboxylic acid group, or sulfonic acid group, a salt or ester thereof or an amine group or salt or amide thereof.

8. A process according to claim 6 or claim 7 wherein said unsaturated segment is a polymer segment having an a, p-ethylenic double bond.

9. A process according to claim 8 wherein said unsaturated segment is polybutadiene, polychloroprene, polyisoprene or an unsaturated polyester and said hydrophobic hard segment is polystyrene, poly methyl styrene, polyethylene, polypropylene, a polyurethane aromatic polyester or a polyamide.

10. A process according to any one of claims 6 to 9 wherein the reaction with the thioalcohol group containing compound is carried out in the presence of an initiator in a solvent.

11. A process according to claim 6 substantially as herein described with reference to the Examples.

12. A hydrophilic polymer made by a process according to any one of claims 6 to 11.