GB1564380A - Paints and printing inks containing block copolymer binder - Google Patents

Description

(54) PAINTS AND PRINTING INKS CONTAINING BLOCK COPOLYMER BINDERS (71) We, DENKI KAGAKU KOGYO KABUSHIKI KAISHA, a corporation organised under the laws of Japan, of F1, Yurakicho 1-chome, Ghiyoda-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to compositions for paints and printing inks having a good coating property and particularly to compositions for paints and printing inks containing a vinylsubstituted aromatic hydrocarbon/conjugated diene block copolymer as a binder, having a good wening to inorganic pigments and good dispersibility of them.

Styrene-butadiene type resins have, hitherto, been used as a binder for paints for concrete, vessels and others and for printing inks, in which such properties as water resistance, chemical resistance and abrasion resistance are required.

Since these styrene-butadiene type resins are usually produced by a radical polymerization method, they have a wide distribution of molecular weight, including a considerable amount of low-molecular weight polymers and, further, have the polymer chain configuration having styrene and butadiene units arranged at random therein. Therefore, the coat or film formed by these resins is markedly deteriorated in mechanical strength and, also, lowered in such properties as water resistance, weather resistance and chemical resistance.

For improving the film strength of styrenebutadiene resins, various methods were proposed, but the products are unsuitable for use as a binder for paints and printing inks. By way of example, a high impact polystyrene with improved film strength is obtained by grafting polystyrene to elastomeric polymers. However, when this resin is dissolved in such a solvent as xvlene and cast as a film, elastomer particles deposit out on the film face and accordingly the film has an extremely poor appearance. Similarly, when ABS resins obtained by copolymerisation with acrylic monomers are dissolved in a solvent such as xylene and cast as a film, gelled elastomer particles deposit out on the surface of the film and so the film has a poor appearance.

On the other hand, it is known that block copolymers having a regulated molecular configuration are obtained by copolymerising vinyl-substituted hydrocarbon and conjugated diene monomers in an anionic polymerisation medium using an alkali metal or organoalkali metal initiator. It is also known that block copolymers with various properties are obtained by varying the molecular weight, the distribution of molecular weight and the composition ratio of monomers. For example, with the styrene/butadiene ratio ranging from about 25/75 to 50/50, the resulting block copolymer is a transparent, thermoplastic elastomer, which is used for, e.g. shoe soles, hot melt adhesives and plastic blends. Block copolymers having the styrene/butadiene ratio of from about 50/50 to 70/30 are transparent, soft resins and can be used for e.g. stretch films and toy materials.Block copolymers having the styrene/butadiene ratio of from about 75/25 to 90/10 are rigid, transparent resins, which have improved properties such as impact resistance and cold resistance.

We appreciated that block copolymers such as styrene/butadiene type resins prepared by anionic polymerisation might have physical properties suitable as the binder matrix of paints and printing inks, and indeed we found that coating compositions containing these resins as the binder give a coat or film having a smooth surface without occurrence of gel and that these coating compositions which are thixotropic have a good coating workability and are useful for anticorrosives. Also, we have found that a printing ink prepared by using these resins as a binder is useful for a specific ink exhibiting a delustering, delicate colour tone. However we also found that it was extremely difficult to achieve satisfactory dispersion of inorganic pigments into such binder matrices.Thius the pigmented film or coat was found to have gloss and water resistance properties inferior to those obtained when the binder was a copolymer obtained by free radical polymerisation.

A paint or ink composition according to the invention comprises a solution of a binder matrix in which a pigment is dispersed, in which the binder matrix carries terminal polar groups and comprises a block copolymer which has been made by anionic polymerisation of a vinyl substituted aromatic hydrocarbon and a conjugated diene.

We are aware that U.S. Patents No.

3,108,994 and 3,135,716 disclose a method for the production of a terminally reactive polymer by reacting living polymers with a suitable reactant, in which mercapto, hydroxy or acidic groups are introduced as the reactive group, and the resulting terminally reactive polymer is used for cross linking. We are also aware that dispersions of titanium dioxide particles in toluene stabilised by partially car boxylated styrene-butadiene block copolymer are reported in Advan. Chem. Ser., Vol. 99, PP 379-396 (1971), "Dispersion of Solid Particles in Organic Media" by G. E. Molan and E. H. Richardson. The carboxylation is effected by adding thioglycolic acid to the main chain of polymers.However the invention provides for the first time the possibility of making a paint or ink composition that will yield good gloss and good water resistance and other mechanical properties when spread as a film, and which in particular combines the need for ease of dispersion of the pigment in the binder matrix and the use of a binder matrix comprising a block copolymer which has the advantages that follow from it having been made by anionic polymerisation, generally anionic solution polymerisation.

Preferred paint and ink compositions accord ing to the invention comprise inorganic pigment dispersed in a binder matrix comprising a block copolymer made by anionic polymer isation of the aromatic hydrocarbon and a diene in the presence of an alkali metal initiator followed by reaction of some or all of the resultant terminal groups containing alkali metal atoms with a compound that yields a polar group containing oxygen, nitrogen or sulphur atoms.

The anionic polymerisation is generally con ducted in solution in the presence of an alkali metal or organo-alkali metal initiator. The conditions may be such that the block co polymer consists of discrete blocks of the indi vidual polymeric components with a clear distinction between one block and the next, or they may be such as to give a merging or tapering effect between the blocks. The paint or ink composition comprises a dispersion of the pigment in a solution of the binder matrix. While the binder matrix may consist solely of the described block copolymer it is often preferred that it is a mixture of the block copolymer containing terminal polar groups with a block copolymer free of such groups. Also as explained below it is not essential that all terminal groups on the block copolymer should be reacted to carry the polar groups.For instance with linear copolymers one terminal group only may be polar although it is often preferred that both should be. With crosslinked copolymers it is preferred that the terminal group or groups should be at the end of long polymeric chains in order that they have most effect, but they can be present on short branch chains although they will generally have less effect.

Fig. 1 is a graph showing the relation between pigment concentration and film gloss in respect of styrene/butadiene block copolymers having polar groups introduced into the polymer chain terminal.

Fig. 2 is a graph showing the relation between pigment concentration and film gloss in respect of styrene/butadiene block copolymers having different molecular weights.

Fig. 3 is a graph showing the relation between pigment concentration and film gloss in respect of block copolymers having different molecular structures.

Fig. 4 is a graph showing the relation between pigment concentration and film gloss in respect of block copolymers having different polar groups introduced into the polymer chain terminal.

Fig. 5 is a graph showing the relation among pigment concentration, film gloss and content of polymers having polar groups introduced into the polymer chain terminal in respect of block copolymers.

Fig. 6 is a microphotograph of titanium oxide (rutile structure) used as a pigment.

Fig. 7 is a microphotograph of a film formed by a coating composition of polymers containing no terminal polar groups and titanium oxide.

Fig. 8 is a microphotograph of a film formed by a coating composition of polymers containing terminal carboxyl groups and titanium oxide.

When polar groups containing oxygen, nitrogen or sulphur are introduced into the terminals of polymers obtained by an anionic, preferably solution, polymerization, wetting of the resulting polymers to pigments is remarkably increased and surprisingly, remark able effect in improvement of dispersibility of inorganic pigments can be found though the amount of polar groups containing in whole polymers is quite small. Moreover, a remarkable effect can be attained also in improvement of various physical properties such as gloss and water resistance of the coating film of coating compositions obtained by compounding a pigment of practical concentration.

Further, when using the resin as a binder of a composition for printing ink, it is recognized that remarkable effects can be attained in improvement of mechanical strength and gloss of the coated film and storage stabilization of the ink.

The vinyl-substituted aromatic hydrocarbon which may be used includes, for example, styrene and various alkyl styrenes such as ernethyl styrene, vinyl toluene, tert. -butyl styrene and their similar materials and mixtures thereof. Also, the conjugated dienes which may be used include, for example, butadiene, isoprene and their similar materials and mixtures thereof. Morover, the polymer which may be used in this invention is a block copolymer consisting of polymers of the abovementioned monomers, which is from soft to hard resinous polymer having such a block structure as shown below.

The composition ratio of vinyl-substituted aromatic hydrocarbon to conjugated diene in the block copolymer is not particularly limited, but the ratios of about 50--95 to 5S5 are preferable, preferably 75 to 90%.

The structures of suitable block copolymers are represented by (A--B),, (A-B),,-A, and (A--B),X, wherein A is a polymer comprising mainly vinyl-substituted aromatic hydrocarbon units, and B is a polymer comprising mainly conjugated diene units.

However, it may be permitted that a small amount of conjugated diene is copolymerized with sequence A and a small amount of vinylsubstituted aromatic hydrocarbon is copolymerized with sequence B. n is an integer of 1 to 10 and X is a residue of a coupling agent having more than two functional radicals or of a polyfunctional polymerization initiator.

Sequences A and B of the above-mentioned structure may be linked by a clearly cut linkage and also, may be in the form of a tapered copolymer which is disclosed in US Patent No. 3,947,536.

Alkali metals which may be used as polymerization initiators include for example, lithium, sodium, and potassium. Further, as organo alkali metal compounds, naphthalene complexes of such a metal as lithium, sodium and potassium, or alkyl or aryl alkali metal compounds such as butyl lithium can be used.

Moreover, polyfunctional initiators such as organodilithium compounds and organopolylithium compounds may be used.

When polymerization is carried out using an organic monolithium compound, polymers produced by treating with a polar reactant have such a structure that the polar group is introduced into only one terminal of the polymer chains. Then, in the case of using an organodilithium compound, polymers produced by reacting with a polar reactant after polymerization have such a structure that polar groups are linked to both terminals of the polymer chains.

Further, in the case of employing a polyfunctional initiator, branched star polymers are produced, and polymers prepared by reacting the branched star polymers with a polar reactant have such a structure that polar groups are introduced to each terminal of the branched polymer chains of the star polymers.

The effect of the terminal polar group will vary depending on the structure of the block copolymer and the proportion of the polymers having terminal polar groups in the total binder matrix. For example, when polymerisation is carried out by using a polyfunctional initiator to introduce polar groups into many terminals of polymer chains, it has been found that effects of the introduced polar groups become more remarkable than in the case of introducing a polar group into only one terminal.

It has, also, been found that polymers containing the polar group at the centre of the polymeric chain, which are produced by linking a linear polymer with a polyfunctional coupling agent, for example divinyl benzene, to prepare a star polymer, and reacting the star polymer with a polar reactant attain smaller effect of the polar group than polymers containing polar groups at polymer chain terminals.

Suitable block copolymers are produced by anionic polymerisation at any suitable temperature under an inert atmosphere and in the presence of a polymerisation solvent. Suitable solvents include benzene, cyclohexane, toluene, xylene ethylbenzene, tetrahydrofuran, ethylcyclohexane, methylcyclohexane and mixtures thereof.

Polar reactants which may be used in this invention include materials capable of reacting with the terminal alkali metal thereby imparting a hydrophilic polar group containing oxygen, nitrogen or sulphur into polymer chain terminals.

Examples of these oxygen-, nitrogen- or sulphur-containing reactants are as follows: 1) Reactants for introducing a carboxyl radical; Carbon dioxide.

2) Reactants for introducing a hydroxyl radical; Oxygen, sulphur dioxide, ethylene oxide, porpylene oxide, styrene oxide, aldehydes, ketones, halohydrins and diepoxybutane.

3) Reactants for introducing a thiol radical; Sulphur, carbon disulfide and alkylene sulfides.

4) Reactants for introducing an amino radical; Alkyleneimines.

5) Reactants for introducing a sulfone radical; Sulfuryl chloride.

6) Reactants for adding acid anhydrides; Maleic anhydride, succinic anhydride and phthalic anhydride.

7) Other reactants for adding polar compounds: Phosgene, thionyl chloride, cyanogen halides, cyanogen, toluene 2,4-diisocyanate, cyclic disulfides, p-bromoaniline, ethyl adipate and ethyl sebacate.

The polar group may also be introduced by polymerising several molecules of an anionically polymerisable polar monomer onto vinyl-substituted aromatic hydrocarbon-conjugated diene block copolymers at their polymer chain terminals.

Examples of these polar monomers are epoxides such as ethylene oxide and propylene oxide; alkylene sulfides such as ethylene sulfide and propylene sulfide; acrylates such as isopropyl acrylate; methacrylates such as methyl methacrylate, ethyl methacrylate, hexyl methacrylate and allyl methacrylate; vinyl pyridine; siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotrisiloxane and octamethylcyclotetrasiloxane; 1,2-dihydronaphthalene, 1methacryloxy-2-butyne and formaldehyde.

As a reference to such polar reactants there is, for example, indicated " Synthesis of Block Polymers by Homogeneous Anionic Polymerization" L. J. Fetters, J. Polymer Sci. Part c, No. 26, pp 1-35 (1969).

Polar groups thus introduced into polymer chain terminals have great effect even though they are not introduced to all the terminals.

For example, in the reaction of polymers containing terminal alkali metal with polar reactants, a side reaction such as coupling between polymer molecules may occur in some cases depending on reaction conditions, e.g. type of polar reactants, structure of polymers, solvents, a reaction temperature and a reaction vessel.

Further, when the coupling reaction takes place during the reaction with the polar reactant after the polymerization with use of the polyfunctional initiator, the resulting polymers are allowed to gel so that the reaction amount between the polymer containing terminal alkali metal and the polar reactant is extremelv reduced. One of the characteristics of this invention, however, is that the effects of introducing polar groups can be attained when polar groups are introduced into at least a part of the polymer chain terminals even though not introduced into all of the terminals due to the side reaction such as the coupling reaction.For example, when an anionic solution polymerization is carried out in benzene by using an organodilithium initiator to obtain polymers containing alkali metals at both terminals and then polar groups are introduced by feeding carbon dioxide gas into the resulting polymer solution at about room temperature, the polymer solution may be immediately allowed to gel so that polar groups cannot be introduced into all of the terminals of the polymer chain. As a result only a small amount of polar groups may be introduced by such a method. However best results are generally obtained if polymers containing terminal polar groups are more than about 4 by weight of the polymers in the binder matrix.

Moreover, when a solution polymerisation accompanied with a side reaction such as chain transfer is carried out in a polymerisation solvent such as toluene and then a polar reactant such as carbon dioxide gas is fed into the resulting polymer solution, the amount of polar groups introduced into terminals of the polymer chain is quite small. However it has again been found that best results are obtained if polymers containing terminal polar groups account for more than about 4% by weight of the polymers in the binder matrix.

It is theoretically possible for 100% of the polymers in the matrix to be polymers having polar groups terminally introduced, but the amount is usually within the range of about 4 to 60% by weight of the polymers in the matrix.

These polymers containing terminal polar groups can be produced by various methods.

For example, polymers having lithium carboxylate at both terminals can be produced by polymerizing styrene with butadiene in xylene in a nitrogen atmosphere by use of an alkyl dilithium initiator and feeding carbon dioxide gas into the resulting polymer solution.

The polymer solution thus obtained may be compounded with pigments to prepare coating compositions. Before the preparation, however, it is desirable to add an excess of water or alcohols or other Lewis acids to the polymer chain terminals to reduce a viscosity of the polymer solution.

Further, thus produced polymers may be separated by depositing with methanol or steam stripping and taken out as dried powders to prepare a coating composition.

Suitable inorganic pigments that can be dispersed in the matrix include various metals, metal oxides, metal sulfates, chlor- mates and metal carbonates and others, Examples are titanium oxide, zinc white, white lead, lithopone, white alumina, precipitated barium sulfate, finely powdered silicic acid, iron black, red oxide, silver vermilion, red copper oxide, molybdate chrome orange, chrome yellow, zinc chromate, chromium oxide, prussian blue, ultramarine and aluminium powder. Carbon black can also be used.

Compounding is carried out in an organic solvent by means of a conventionally employed stirrer, such as ball mill and Attritor Mill.

The amount of the inorganic pigment is properly adjusted depending on the objective coated film, molecular weight of the polymer having polar groups and materials to be compounded. Generally, a pigment concentration is within the range of 5 to 80% by volume, preferably 10 to 50 /O by volume. A wide variety of solvents may be used for the coating composition, but non-polar solvents often give especially desirable effects. Suitable solvents include vinyl aromatic compounds such as xylene, ethylbenzene, and toluene, alicyclic compounds such as ethylcyclohexane and other materials such as petroleum constituent represented by mineral spirit.

The coating composition containing these solvents has a moderate thixotropy and storage stability (hardly separated). However any suitable solvents which can dissolve the resin may be used as also may mixtures.

This invention will be illustrated by the following Examples.

Example 1.

AB type block copolymer (A: polystyrene, B: pelybutadiene) was produced by an anionic living polymerization in a nitrogen atmosphere with use of benzene as the polymerization solvent and secondary-butyl lithium as the initi ator. As the polymerization vessel was used a glass autoclave having a capacity of 2 1. 1200 g.

of a well dried benzene and 255 g. of styrene were fed into the autoclave and further, 45 g.

of a purified butadiene were dissolved in the benzene-styrene mixture solution. A solu tioa of 6.0 millimoles of secondary-butyl lithium in heptane was added while maintaining the temperature in the polymerization vessel at 20 C.

The temperature was raised up to 60 C.

After about 60 minutes, polymerization of butadiene and styrene was completed and the content was colored in red. Further, BAC type block copolymer containing terminal carboxyl groups (C: carboxyl group) was produced by feeding into the above red solution of AB type block copolymer carbon dioxide gas at the flow rate of about 10 1 per minute. Polymer powders were prepared by separating polymers from the polymer solution by means of the steam stripping method.

As the results of analysis, it was found that both the AB type and BAC type block copolymers were block copolymers having a number average molecular weight of 5 X 10i, consisting of polystyrene of 85% by weight and polybutadiene of 15% by weight. As to the BAC type block copolymer, polymers containing terminal carboxyl groups were about 50 /O of the whole polymers, according to a thin layer chromatography. Also, according to a NMR analysis both of AB type and BAC type block copolymers were tapered block copolymers containing a little region consisting of styrene butadiene random copolymers.

Next, two compositions were prepared by mixing each of the above AB type and BAC type block copolymers with titanium oxide (rutile structure) and xylene by means of a ball mill for about 10 hours. On a well washed steel plate was each of the two compositions applied by means of a film applicator and dried at room temperature for two weeks. A specular reflectance at 60 (gloss degree) was measured in respect of the coated film. The results are given in Fig. 1. It is clear from Fig.

I that the polymer containing terminal carboxyl groups (Curve BAC) is quite superior in film gloss to the polymer containing no terminal carboxyl group (Curve AB).

Example 2.

Three BAC type block copolymers containing terminal polar groups and having a number average molecular weight of 3 X 104, 5 X 104 and 10 X 104, respectively, composed of 85% by weight of styrene and 15% by weight of butadiene were produced varying the amount of the initiator by the same anionic living polymerization as in Example 1.

For comparison, three BA type block copolymers containing no terminal carboxyl group, of the same composition as the BAC type, and having a number average molecular weight of 3 X 104, 5 X 104 and 10 X 104, respectively were produced in the same manner as in Example 1. Each copolymer was compounded with a titanium oxide pigment (rutile structure) and xylene by means of a ball mill according to the same method as in Example 1. The relation between pigment concentration and film gloss was measured. The results are shown in Fig. 2.

It is apparent from Fig. 2 that in any case of copolymers having different molecular weights the BAC type polymers containing a carboxyl group at one terminal of the polymer have superior film gloss to that of the AB type polymers containing no polar group under the same concentration of the pigment.

Example 3.

(1) BAC type tapered block copolymers containing terminal carboxyl groups and having a number average molecular weight of 50,000 composed of 85% by weight of styrene and 15% by weight of butadiene, and AB type tapered block copolymers containing no terminal polar group, of the same composition were produced according to the same anionic living polymerization as in Example 1.

(2) CABAC type tapered block copolymers containing carboxyl group at both terminals of the polymer and having a number average molecular weight of 50,000, composed of styrene of 85 by weight and 15% by weight of butadiene, and ABA type tapered block copolymers containing no terminal polar group, of the same composition were produced employing a butadiene oligomer dilithium initiator by the same anionic living polymerization as in Example 4.

(3) A star polymer was prepared by producing a linear polymer with use of benzene and a secondary-butyl lithium initiator in a nitrogen atmosphere, and adding a coupling agent.

The polymerization was carried out in a glass autoclave having the capacity of 2 1.

1200 g. of a well dried benzene and 255 g.

of styrene were fed while maintaining the temperature in the autoclave at 200 C, and further a solution of 60 millimols of sec-butyl lithium in heptane was added. As soon as the temperature was elevated to 600 C., the polymerization of styrene advanced and the contents turned to red.

After the temperature was again cooled to 200 C, 45 g of a purified butadiene were blown into the polymer solution. The temperature was elevated to 600 C and maintained for 2 hours. The polymer solution turned slightly to yellow. Then 480 millimols of a 10% benzene solution of a well dried divinyl benzene was fed into the polymer solution while stirring.

The contents in the autoclave became deep red and coupling of linear polymers occurred, thereby to yield a (AB)1 type star block copolymer.

Next, after the above deep red polymer solution was heated up to about 80" C, carbon dioxide gas was blown at the flow rate of about 20 1 per minute, to yield a star block copolymer containing carboxyl groups.

According to the results of analysis, thus produced (AB)1,, type and (ABC)10 type star block copolymers were poly-branched block copolymers having a number average molecular weight of 5 X 104, composed of polystyrene of 85% by weight and polybutadiene of 15% by weight.

(4) Into the above-mentioned AB type tapered block copolymer, ABA type tapered block copolymer, (AB)lo type star block copolymer, BAC type tapered block copolymer, CABAC type tapered block copolymer and (ABC)1. type star tapered block copolymer, respectively were added a pigment (titanium oxide: rutile structure) and a diluent (xylene), and compounding was carried out in the same manner as in Example 1.

The relation between pigment concentration and film gloss is shown in Fig 3.' Curve a: AB type block copolymer, Curve b: ABA type block copolymer, Curve c: (AB)lo type block copolymer, Curve d: BAC type block copolymer, Curve e: CABAC type block copolymer, Curve f: (ABC)1. type block copolymer.

Fig. 3 shows that polymers containing no polar group (Curves a, b and c) are reduced in film gloss at practical concentrations of the pigment; among polymers containing carboxyl groups, the CABAC type polymers (Curve e) containing carboxyl groups at both terminals of the polymers have the highest gloss; and film gloss becomes lower in the order of the BAC type polymers (Curve d) and the (ABC)1., type polymers (Curve f).

It is clear from these facts that the introduction of polar groups into both terminals of polymers is more suitable than that into one terminal of polymers, and the introduction of polar groups into terminals of a linear polymer chain exhibits more desirable effects on film gloss than that into the center of star polymers.

Example 4.

ABA type polymers were produced by effecting an anionic living polymerization in a nitrogen atmosphere, employing xylene as the polymerization solvent and butadiene oligomer dilithium initiator.

As the polymerization vessel, was used a glass autoclave of 2 1 in capacity. 1200 g. of a well dried xylene and 255 g. of styrene were charged. Further, 45 g. of a purified butadiene were dissolved therein.

The temperature in the autoclave was kept at 200 C., and a solution of 6.0 millimols of butadiene oligomer dilithium in benzene was added.

The temperature was elevated to 600 C.

After about 30 minutes, polymerization of butadiene and styrene was completed and the content solution was colored in red.

Moreover, CABAC type block copolymers containing carboxyl group at both terminals of polymer chain were prepared by heating the above-mentioned red polymer solution of ABA type block copolymers at about 100" C., feeding carbon dioxide gas at the flow rate of 20 1 per minute and pouring the resulting polymer solution in much amount of methanol to deposit polymers.

According to the results of analysis, thus prepared ABA type and CABAC type block copolymers are block copolymers having a number average molecular weight of 5 X 104, consisting of polystyrene of 85% by weight and polybutadiene of 15% by weight.

As to the CABAC type block copolymer, polymers containing terminal carboxyl groups was about 50 / of the whole polymers, according a thin layer chromatography.

It was found from the results of NMR analysis that any of the ABA type and CABAC type block copolymers were tapered block copolymers containing the considerable region composed of styrene-butadiene random copolymer.

Next, using each of the above CABAC type and ABA type block copolymers, two compositions were prepared with the formulations as described hereunder in the same manner as in Example 1.

Parts by weight Block copolymers 77 Titanium oxide, rutile structure 63 Xylene 178 Pigment concentration: 15% by volume Each of the compositions thus prepared was applied on a well washed steel plate by means of a film applicator, and the coated film was dried at room temperature.

Fig. 6 relates to a microscopic photograph (X lOS) of titanium oxide (rutile structure), and Fig. 7 and Fig. 8 relate to microscopic photographs (X 103) of the coated films obtained from polymers having no terminal polar group and polymers having terminal carboxyl groups, respectively.

Gloss degrees of the coated films are shown in Table 1.

TABLE I

gloss degree % ABA type block gloss degree copolymer 30 CABAC type block copolymer 100 The gloss degree in Table 1 is indicated by specular reflectance at 60 according to the method of JISK 5400.

It is apparent from Table 1 and Figs. 7 and 8 that the coated film prepared from polymers containing no polar groups has low gloss, and particles of the pigment are aggregated in the coated film, while the coated film prepared from polymers containing terminal carboxyl groups has high gloss and particles of the pigment are uniformly dispersed in the coated film.

Example 5.

Into a red benzene solution containing living polymers consisting of AB type tapered block copolymers produced according to the same method as in Example 1 were blown carbon dioxide gases at about room temperature thereby to produce BAC type polymers containingCOOM groups (M is Li metal or hydrogen) at terminals of the polymer chain.

Also, polymers containingOM groups at terminals of the polymer were produced by blowing a gaseous mixture of oxygen and nitro gen into a benzene solution containing living polymers consisting of AB type tapered block copolymers produced in the same manner as the above.

Similarly, polymers containingSM groups at polymer terminals were produced by adding a 10% benzene solution of carbon disulfide into a benzene solution containing living poly mers consisting of AB type tapered block co polymers.

Similarly, polymers containing five molecules of vinyl pyridine on an average at poly mer terminals were produced by adding a 10% benzene solution of 2-vinyl pyridine into a benzene solution containing living polymers consisting of AB type tapered block copolymers.

Similarly, polymers containing --C,H,Si(OCH,), groups at polymer terminals were produced by adding a 10% benzene solution of y-chloropropyl trimethoxy silane into a benzene solution containing living polymers consisting of AB type tapered block copolymers.

A pigment (titanium oxide : rutile structure) and a diluent (xylene) were added to the above-mentioned AB type tapered block copolymer having a number average molecular weight of 50,000, composed of styrene of 85% by weight and butadiene of 15% by weight, and the above-mentioned five polymers containing polar groups at polymer terminals, of the same composition and molecular weight as the AB type, respectively. Compounding was carried out in the same manner as in Example 1. The relation between pigment concentration and film gloss is shown in Fig. 4.

Curve g: Block copolymer containing no terminal polar group, Curve h: Block copolymer containing termi nal C3HSi(OCH3)3 group, Curve i: Block copolymer containing termi nal -SM group, Curve j: Block copolymer containing terminal vinyl pyridine molecules, Curve k: Block copolymer containing termi nal -OM group, Curve 1: Block copolymer containing termi nal -COOM group.

It is clear from the figure that polymers containing terminal polar groups are extremely superior in film gloss to polymers containing no terminal polar group at the practical con centrations of the pigment.

That is to say, it may be said that dispers ibility of a pigment in any of polymers contain ing terminal polar groups is apparently more excellent than that of the pigment in polymers having no terminal polar group.

Example 6.

AB type tapered block copolymers containing no terminal polar group were produced by the same method as in Example 1.

Next, into thus obtained benzene solution containing living copolymers were fed carbon dioxide gases under such conditions that the content of polymers containing terminal carboxyl groups reached 2%, 5%, 10% and 50%, respectively based on the whole polymers.

These polymers were compounded with with titanium oxide (rutile structure) and xylene in the same manner as in Example 1.

In respect of the compositions, the relation between pigment concentration and film gloss is shown in Fig. 5.

Curve m: Block copolymer containing no terminal carboxyl group, Curve n: Content of polymers containing terminal carboxyl groups, 2% Curve o: do, 5% Curve p: do, 10% Curve q: do, 30% It is clear from the figure that the film gloss becomes higher as the content of polymers containing terminal carboxyl groups increases.

Further, when the content of polymers containing terminal carboxyl groups is near 2% of the whole polymers, the effect on film gloss is not noticeable but it becomes considerably remarkable in case of more than about 4%, as is seen.

Example 7.

The BAC type and AB type block copolymers produced in Example 1, and a polymer of the same composition, having the same viscosity at a 10% xylene solution of polymer (B type viscosimeter, at 250 C), which was produced by a radical emulsion polymerization method were used for the following formulation: Parts by Wight Polymers 20 Titanium oxide (rutile structure) 20 Zinc white 2.0 Disparlon D4200 0.2 (Dispersing agent of polyethyleneoxide type) Chlorinated paraffin 10 (Chlorine content 40%) Xylene 48 The preparation was carried out by means of a ball mill for about 10 hours. Each of the three compositions thus obtained was applied onto a well washed steel plate by means of a film applicator, and dried at room temperature for two weeks. Thereafter, various performance tests on the coated film were effected.

The results are shown in Table 2.

TABLE 2

A* 1) B*2) C*3) Specular gloss at 600, Cle 100 40 100 Adhesion to the substrate *4) Good Quite Good bad Impact resistance *5) Good Good Quite bad Resistance to salt water *6) Good Quite Bad (3% salt water, 200 hours) bad Resistance to salt-fog *6) Good Quite Bad (5% salt water spray, 200 hours) bad Accelerated weather resistance *6) Good Good Quite (600C, carbon arc, 100 hours) bad Notes:: *1) Coated film of the composition of polymers containing terminal polar groups.

*2) Coated film of the composition of polymers containing no terminal polar groups.

*3) Coated film of the composition of polymers which were prepared by a radical emulsion polymerization.

*4) Measured according to a cross-cut adhesion test.

*5) Measured by dropping a steel ball-of 6.35 mmss on a steel plate of 1 mm in thickness coated with a test film from 50 cm high and rating change of the film with the naked eye.

*6) Rated by observing the film surface with the naked eye As being clear from the Table 2, the coated film of this invention is quite superior in gloss, adhesion to the substrate, a saline solution resistance, and a salt-fog resistance to the coated film composed of copolymers containing no terminal polar group.

Further, it is apparent that the coated film of this invention has a quite excellent performance in the impact resistance and accelerated weather resistance, and also has an excellent performance in the saline solution resistance and saline solution spray resistance, compared with the coated film composed of styrenebutadiene copolymers produced according to a radical emulsion polymerization method.

Example 8.

The BAC type and AB type block copolymers produced in Example 1, and a random copolymer of the same composition having the same viscosity at a 30% xylene solution of polymer (300 cps, B type viscosimeter at 20 C), which was produced by a radical polymerization were used, respectively, as a binder for a blue ink.

Using phthalocyanine blue as a pigment, three compositions were prepared by means of a ball mill according to the following formulation.

Parts by weight Pigment (phthalocyanine blue) 3 Calcium carbonate 10 Polymer 20 Solvent (Xylene) 67 The ink compositions thus obtained have physical properties as set forth in Table 3.

TABLE 3

Copo lymers BAC type AB type Radical polymzn.

Items products Storage stability Good Good Quite bad (after one day) (after one day) Storage stability Good Quite bad Quite bad (after one week) Film strength Good Good Quite bad Film gloss Good Quite bad Good Hiding power Good Quite bad Quite bad Graininess Not found Found Not found In the ink with use of the radical polymerization product, precipitates of a white calcium carbonate were observed one day after the preparation of the blue ink.The blue ink with use of the AB type block copolymers as the hinder, one week after the preparation, was separated into two layers; i.e. a colorless transparent, upper layer and a blue, lower layer.

From the above table, it is apparent that the BAC type block copolymer containing terminal carboxyl groups has the best storage stability as a binder.

Further, the blue ink with use of block copolymers containing terminal carboxyl groups exhibits the best performance in film strength, film gloss, hiding power and graininess in ink, as shown in Table 3.

WHAT WE CLAIM IS: 1. A paint or ink composition comprising a solution of a binder matrix in which a pigment is dispersed, in which the binder matrix carries terminal polar groups and comprises a block copolymer which has been made by anionic polymerisation of a vinyl substituted aromatic hydrocarbon and a conjugated diene.

2. A composition according to claim 1 in which the block copolymer has been made by anionic polymerisation of the hydrocarbon and diene in the presence of alkali metal initiator followed by reaction of some or all of the resultant alkali metal atoms in the polymer with a compound that yielded polar groups containing oxygen, nitrogen and/or sulphur atoms.

3. A composition according to claim 2 in which the compound was a monomer that was polymerised onto the block copolymer and provided the polar groups.

4. A composition according to claim Z m which the compound was a monomer that yielded carboxylic, hydroxyl, thiol, amino, sulphone or acidic anhydride groups.

5. A composition according to claim 4 in which the compound was carbon dioxide.

6. A composition according to any preceding claim in which the block copolymer was made by solution polymerisation.

7. A composition according to any preceding claim in which the block copolymer is substantially linear and both terminal positions carry polar groups.

8. A composition according to any preceding claim in which the binder matrix comprises more than 4% of the said block co polymer carrying polar groups based on the total weight of polymer in the matrix.

9. A composition according to claim 8 in which the polymers of the binder matrix comprise 4 to 60% by weight of the block copolymer carrying polar groups and 96 to 40% by weight of a block copolymer of a vinyl substituted aromatic hydrocarbon and a conjugated diene and which is free of polar groups.

10. A composition according to any preceding claim in which the aromatic hydrocarbon is styrene and the conjugated diene is butadiene.

11. A composition according to claim 1 substantially as herein described with reference to any of the Examples.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. TABLE 3 Copo lymers BAC type AB type Radical polymzn. Items products Storage stability Good Good Quite bad (after one day) (after one day) Storage stability Good Quite bad Quite bad (after one week) Film strength Good Good Quite bad Film gloss Good Quite bad Good Hiding power Good Quite bad Quite bad Graininess Not found Found Not found In the ink with use of the radical polymerization product, precipitates of a white calcium carbonate were observed one day after the preparation of the blue ink.The blue ink with use of the AB type block copolymers as the hinder, one week after the preparation, was separated into two layers; i.e. a colorless transparent, upper layer and a blue, lower layer. From the above table, it is apparent that the BAC type block copolymer containing terminal carboxyl groups has the best storage stability as a binder. Further, the blue ink with use of block copolymers containing terminal carboxyl groups exhibits the best performance in film strength, film gloss, hiding power and graininess in ink, as shown in Table 3. WHAT WE CLAIM IS:

1. A paint or ink composition comprising a solution of a binder matrix in which a pigment is dispersed, in which the binder matrix carries terminal polar groups and comprises a block copolymer which has been made by anionic polymerisation of a vinyl substituted aromatic hydrocarbon and a conjugated diene.

2. A composition according to claim 1 in which the block copolymer has been made by anionic polymerisation of the hydrocarbon and diene in the presence of alkali metal initiator followed by reaction of some or all of the resultant alkali metal atoms in the polymer with a compound that yielded polar groups containing oxygen, nitrogen and/or sulphur atoms.

3. A composition according to claim 2 in which the compound was a monomer that was polymerised onto the block copolymer and provided the polar groups.

4. A composition according to claim Z m which the compound was a monomer that yielded carboxylic, hydroxyl, thiol, amino, sulphone or acidic anhydride groups.

5. A composition according to claim 4 in which the compound was carbon dioxide.

6. A composition according to any preceding claim in which the block copolymer was made by solution polymerisation.

7. A composition according to any preceding claim in which the block copolymer is substantially linear and both terminal positions carry polar groups.

8. A composition according to any preceding claim in which the binder matrix comprises more than 4% of the said block co polymer carrying polar groups based on the total weight of polymer in the matrix.

9. A composition according to claim 8 in which the polymers of the binder matrix comprise 4 to 60% by weight of the block copolymer carrying polar groups and 96 to 40% by weight of a block copolymer of a vinyl substituted aromatic hydrocarbon and a conjugated diene and which is free of polar groups.

10. A composition according to any preceding claim in which the aromatic hydrocarbon is styrene and the conjugated diene is butadiene.

11. A composition according to claim 1 substantially as herein described with reference to any of the Examples.