NO131428B - - Google Patents

Description

Process for the production of a vesicular cross-linked polyester resin granulate.

The present invention relates to a method for producing a vesicular polymer granulate as well as the vesicular granulate thus produced.

By vesicular polymer granules is meant a polymer granule that contains a majority of cells or small vesicles (vesicles). The ideal is that the vesicles are completely encapsulated in a polymer shell, i.e. that the polymer granules do not have a continuous porosity extending from one cell to the other, but consist of a plurality of separate, isolated vesicles. There may be a small proportion of imperfect vesicles where some of the polymer shell is not formed or is broken, allowing passage from one vesicle to its neighboring vesicle.

It has now been found that it is possible to produce vesicular polymer granules of predetermined dimensions, since the granules

in

contains vesicles of exceptionally uniform and small diameter,

from certain unsaturated polyester resins which are cross-linked by an addition polymerization reaction with an unsaturated monomer by a process described below. The granules thus formed are insoluble in many organic liquids and are particularly useful as components for making polymer films and surface coatings opaque.

Carboxylated unsaturated polyester resins which react with a polymerizable unsaturated monomer to provide a crosslinked resin are well known in the art, as are methods of initiating the polymerization reaction. It has now been observed that this reaction can be carried out in small globules of a solution of an unsaturated polyester resin in a polymerizable monomer suspended in an aqueous liquid to provide a cross-linked polyester resin granulate. Moreover, it has been surprisingly found that if the polyester resin is selected at the below-

for the described sample, a cross-linked granule can be produced where a vesicular structure is formed.

According to the invention, a method for the production of a vesicular, cross-linked polyester resin granulate has been provided in that a solution of a carboxyl group-containing unsaturated polyester resin, selected as indicated below, in a

nearly water-insoluble, polymerizable, unsaturated monomer is suspended as discrete spheres in an aqueous continuous phase in the presence of from 0.3 to 10 equivalents per carboxyl group of a base having a dissociation exponent less than 8, and the polymerization is initiated to crosslink the polyester resin.

By an almost water-insoluble monomer is meant a monomer which at 25°C has a solubility in water approximately the same as styrene and vinyltoluene.

The vesicles are formed in the granulate by entrapment of droplets of aqueous liquid that spontaneously form within the dispersed polyester resin solution. especially when a granule with a large vesicle volume is required, droplets of an aqueous liquid can pre-disperse

es in the polyester resin solution before this solution itself is dispersed in the continuous phase to enlarge the vesicles which momentarily

bodies are formed. Essentially, gas-containing vesicles are formed when the contained liquid is expelled from the granulate by e.g. allowing it to dry in air until the liquid has diffused out of the vesicles.

The unsaturated polyester resin used in the present invention is selected from condensation polymers which provide both polymerizable unsaturation for co-reaction with the unsaturated monomer and carboxyl groups which react with and are at least partially neutralized by the added base". The polyester resin and the polymerizable monomer are initially linked on

known way, bearing in mind the degree of hardness required in the cross-linked granulate. In general, the cross-linked resin should be a hard solid at room temperature. Unsaturated esters of this general type are well known, but it is also required that the polyester used in the method according to present

end invention, is selected in the following selection test. The resin must primarily be soluble in xylene. If necessary, mix-

none is heated to facilitate the preparation of a workable solution

nothing. To a solution of the sample polyester in xylene, 5% by weight aqueous ammonia solution is added with moderate stirring. The amount of ammonia

akk is a molar equivalent based on the acid number of the resin and the total solids of the polyester solution in xylene is equal to that of the resin solution in the monomer used to make the granulate. The mixture is then examined under an optical microscope.

If the resin is suitable for the production of cross-linked, vesic-

learned granules according to the present invention, a stable dispersion of drops of aqueous liquid will be seen to be formed in the resin solution. The droplets are often of submicron size, but provided the mixture is substantially free of dispersed particles larger than 5 microns and remains so for up to 30 minutes, the resin is considered satisfactory for present purposes. The presence of a random and isolated larger drop has no appreciable signifi-

nothing. If an unstable dispersion is formed or the dispersed particles have diameters considerably greater than 5 microns, the unsaturated polyester is not satisfactory for the present purpose,

In practice it has been found that when the polyester resins are examined

in this way, they clearly fall within one of two categories and

can be easily separated in this way. The preferred resins for making granules with very small vesicles are those which are seen to contain substantially dispersed submicron particles when examined by the above test.

No clear relationship has been found between or corresponding limitation on the composition of the polyester resin and the results of this selection test, but in general it is observed that the resin should have a viscosity (such as 70 weight solution1

in xylene) of at least Gardner-Holdt E and an acid value of 5-75 mg KOH/g. Preferably, the viscosity should be greater than Gardner-Holdt S and

in

acid number 10-50 mg KOH/g.

The selected polyester resins are condensation pro-

compounds of polyhydric acids (or the corresponding anhydrides) and dihydric alcohols. Polymerizable unsaturation can be introduced into the molecule by choosing a c{ , y?-ethylenic unsaturated acid, possibly in combination with a saturated acid or anhydride.

Suitable acids are thus, for example:

unsaturated aliphatic acids, e.g. malein-, fumar-, itacone-,

citraconic and mesaconic acids, saturated aliphatic acids, e.g. malonic, succinic, flutaric, adipic, pimelic, azelaic and sebacic acids, and saturated aromatic acids, e.g. phthalic, isophthalic, terephthalic, tetrachlorophthalic, tetrahydrophthalic, trimellitic, trimesic and chloroedic acids.

Suitable divalent alkanols are chosen, for example, from: ethylene glycol, poly(ethylene glycols) e.g. diethylene glycol, hexane-1,6-diol, propylene glycol, dicyclohexanol and neopentyl glycol. Alternatively, the alcohol may be one that originally contained wood

or more hydroxyl groups, as the groups beyond two have been part-

preferably with, for example, a monohydric alcohol, e.g. methanol, ethanol and n-butanol, or esterified with a monovalent acid, e.g. benzoic acid, p-tert-butylbenzoic acid and saturated and unsaturated aliphatic acids with up to 18 carbon atoms in the chain. Alternatively, the dihydric alcohol can be used in the form of an alkylene oxide, e.g. ethylene oxide and propylene oxide.

The processes by which unsaturated polyesters of this

type is assembled and produced is well known in the field.

The polyester resin solution can optionally be pigmented in the usual way to achieve special physical properties, e.g. to increase the granulate's opacity effect or to achieve different color effects. The selected pigments must be water-insoluble and the addition of materials known to prevent free radical polymerization must be avoided. As described below,

pigment can also be introduced into the vesicles.

As mentioned above, the unsaturated monomer with which the polyester resin is dissolved and crosslinked must be approximately water-soluble

corpse. A single monomer or a mixture of monomers can be used for the present purpose and generally the monomer contains only a single polymerizable double bond. However, it is known that polyfunctional monomers, i.e. monomers containing more than one polymerizable double bond, are also usable for crosslinking unsaturated polyester resins. Such polyfunctional monomers

is, however, normally only used as a minor part of the monomer mixture, the main part being made up of the monofunctional monomer. Such monomer mixtures can be used in carrying out the present invention.

The preferred monomers for use in the present invention are selected from styrene, o(-methylstyrene, vinyltoluene and divinylbenzene.

However, the implementation of the invention is not limited to the above-mentioned monomers alone. Only one has in mind that all

monomer must be virtually insoluble in water and also be a solvent for the unsaturated polyester resin, a smaller proportion of other polymerisable, unsaturated monomers may also be present, e.g. to modify the physical properties of the co-reacted resins. Typical comonomers are, for example, esters of acrylic and methacrylic acids, e.g. methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, acrylonitrile, vinyl acetate, tetra-allylethoxy-

ethane, ethylene glycol dimethacrylate and triallyl cyanurate.

Optionally, a few percent by weight of a non-polymerizing organic liquid, e.g. n-butanol, mixed with monomer-

one to increase the solubility of the polyester resin therein.

The aqueous continuous phase is primarily

water, but it is common practice when producing aqueous dispersions or suspensions to add surfactants and possibly polymer thickeners to the continuous phase to stabilize the system. Consequently, in the process according to the invention, a surfactant is often used in the aqueous continuous phase which can be selected from such materials as are known to stabilize suspensions of the oil-in-water type. For example, the surfactant can be of the well-known class in which a polyalkylene oxide chain is attached to an alkyl

phenolic, e.g. nonylphenol-, group. Alternatively, a water-soluble, partially hydrolysed polyvinyl acetate can be used, typically with a molecular weight of 100,000.

If insufficient surfactant is used, the resulting suspension may become unstable. If excess is used, complete emulsification will occur with loss of separate globules of polyester resin solution. As a general guideline, it has been found that a weight concentration of 0.01-0.5% by weight of surfactants of the polyvinyl acetate type in the aqueous continuous phase usually gives satisfactory results.

It has also been found desirable to introduce into the aqueous

in

continuous phase a soluble polymeric material to increase its viscosity. An increase in the viscosity of the aqueous continuous phase prevents settling of suspended spheres and promotes the formation of smaller spheres of polyester resin solution. Suitable thickeners are, for example, water-soluble ethers of cellulose, especially hydroxyethyl cellulose. They are often used in concentrations of 0.02-1.0% by weight of the aqueous liquid.

The base used in carrying out the invention must

be a strong base, by which is meant a base which is at least partially capable of ionizing the carboxyl groups in the unsaturated polyester resin to give a stable aqueous dispersion of the polyester. In general, such a base will have a dissociation exponent of less

than 3, preferably less than 5. By a dissociation exponent is meant ~^-°9ioKb/ ^vor ^ is Dasen's dissociation constant in water at 2 5°C. Suitable strong bases are, for example: inorganic bases such as lithium, potassium, sodium and ammonium hydroxides and their corresponding carbonates; water-dispersible aliphatic amines such as primary amines, e.g. methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine and isobutylamine; secondary amines, e.g. dimethylamine, diethylamine, di-n-propylamine, di-isopropylamine, di-n-butylamine and di-isopropylamine; tertiary amines, e.g. trimethylamine, triethylamine, methyldiethylamine, ethyldimethylamine, n-tripropylamine and isotripropylamine; hydroxyamines, e.g. ethanolamine, diethanolamine and N-methylethanolamine; cyclic amines, e.g. morpholine, pyrrolidine and piperidine; and polyamines, e.g. ethylenediamine, diethylenetriamine, triethylenetetramine, n-propylenediamine, n-hexylenediamine and methanediamine.

Mixtures of the above bases can also be used.

The most useful base is ammonium hydroxide. The

however, it has been found that when granules of the order of 5 microns or less and containing submicron vesicles are to be prepared, the best results are often obtained by selecting an alkali metal carbonate, at least as a major portion of the neutralizing base.

When larger granules are to be produced, but very fine vesicles are required, it is preferred to use a base consisting of at least 10% by weight of a polyamine of the above type. A smaller proportion of non-preferred bases can be tolerated in combination with the preferred bases.

The amount of base required to form stable dispersions of the unsaturated polyester resin solution in the aqueous continuous phase is dependent on the free carboxyl groups in the resin. The minimum amount of base used is 0.3 equivalent base per carboxyl group and to achieve the best results 0.7 equivalent base per carboxyl group. At base concentrations approaching 10 equivalents per carboxyl group, the dispersion of spheres of polyester resin solution in the aqueous continuous phase tends to become unstable, and in general it has been found that a maximum concentration of 3 equivalents of base per carboxyl group is a desirable upper limit.

The granulate can be prepared by first suspending

a solution of the chosen polyester resin in the monomer (typically 40

to 80% resin by weight) in the aqueous continuous phase and in the near-

be off base under continuous mechanical stirring. Small droplets of aqueous liquid are instantly formed inside the suspended spheres of polyester resin solution and consequently provide vesicle-

one in the cross-linked polyester granulate. The size of the suspended globules of polyester resin solution regulates the size of the final vesicular granules by the following factors. The formation of smaller spheres is promoted by high agitation rates and increased viscosity of the aqueous liquid. Increased viscosity of the polyester resin solution generally promotes the formation of coarser spheres. The size of the separated small droplets that provide the vesicles is affected to a certain extent by the choice of base and unsaturated polyester resin and by the concentration of any dissolved material in the aqueous continuous phase, presumably due to osmo-

tical effects. If the separate small droplets formed inside the spheres of polyester resin solution do not have the required size, in practice the composition of the base is varied along the lines indicated above to achieve a more satisfactory size of the small drops of aqueous liquid. Alternatively, it may also be necessary to vary the composition of the resin, e.g. by controlling its viscosity or acid number to provide the desired droplet size. The base, possibly dissolved in water, can be pre-mixed with the polyester solution or added to the aqueous continuous phase before or after the addition of the polyester resin solution.

A preferred method that is particularly useful

for the production of granules with a large vesicle volume or where pigment is to be incorporated into the vesicles, is to disperse drops of a solution of the selected base in water, possibly with added pigment,

in the unsaturated polyester solution and then suspend this product,

under mechanical stirring, in the aqueous continuous phase. On

in this way a suspension of spheres of polyester resin is formed

solution in the aqueous liquid and within each such sphere a dispersion

in

of small droplets of aqueous liquid.

The polymerization is initiated inside the spheres by means of a free-radical initiator, e.g. an organic peroxide or bis-azonitrile or by exposing the beads to a radiation source, such as radioactive cobalt or ultraviolet irradiation. When an organic source of free radicals is used, this is conveniently introduced into the reactants by dissolving it in the monomer or polyester solution before the ball suspension is prepared. The vesicular granules thus formed can be separated mechanically from the aqueous continuous phase and dried or it can be incorporated as an aqueous slurry directly into suitable aqueous compositions. In both cases, loss of water from the granulate will eventually provide essentially air-filled vesicles, in which form it exerts its maximum opacity effect.

With the method according to the invention, it will be possible to form granules with diameters from 0.1 to 500 microns and with vesicle diameters varying from 0.01 to 5.0 microns. However, the maximum achievable diameter of the granules is not limited to 500 microns and for special purposes granules with diameters of up to 2-3 mm can be produced by regulating the ball size that can be formed. Each granule will on average contain more than one vesicle and when the granule is intended for use as an opacifier, the vesicles, which may occupy from 5 to 75%, preferably 10 to 50%, of the granule volume, should have diameters within the range of 0.015 to 5.0 microns , preferably 0.03 to 1.0 microns.

The vesicular polymeric granules according to the present invention can be used as a lightweight filler and opacifier in plastic moldings, polymer films and paper. For these purposes, it is preferred to use the granulate in proportions of up to 25% by volume of the products. When used as a filler, the vesicular granules preferably have a diameter of at most 50 microns. Their opacity effect is greatest with diameters of up to 5 microns.

Large network porous granules are particularly useful as components in plastic moldings used as building cladding and structural parts. For these purposes it is preferred to use

large granules of the order of 2-3 mm and with a vesicle content of up to 80% by volume of the granulate. When encased in molded plastic articles of this type, air-filled granules of said dimensions will make the articles exceptionally light. This is partly due to the possibility inherent in the present method to select the granules' size distribution in advance in order to achieve

j

maximum filling in the plastic base material in which they are enveloped.

In contrast to foamed articles produced by an in situ sludging process, the use of the present granules enables the production of porous articles with a predetermined concentration and size of voids and consequently an exceptionally uniform structure.

Furthermore, it is usable as a matte texturizing, matting and opacity agent in paint products. Granules with an average diameter of from 50 to 500 microns or more can be used to achieve texturing effects in paint films, while if the average diameter of the granules is generally within the range of 1 to 100 microns, the texturing effect becomes less pronounced and the granules can be used to achieve opacity - and matting effect in matt and semi-matt paint. To obtain the best results in semi-matte paints, especially matte aqueous latex paints, it is preferred that the granules have a diameter substantially from 1 to 50 microns and with an average volume diameter of from 5 to 35 microns. The average volume diameter is defined by the expression

where v<1> is the volume fraction of all particles with diameter d1.

Matte paints containing granules with a lower average volume diameter than 5 microns tend to show gloss in the applied paint film and if the average volume diameter exceeds 50 microns, the film's surface appearance is marred by coarse particles that break the otherwise smooth, matte surface.

Granules, with a diameter in the range of 0.1 to 5 microns, are particularly useful in glossy and semi-gloss paints. Because of their vesicular structure, such granules impart opacity to the paint films in which they are enveloped. In contrast to the use of ordinary opacifying pigments, this opacity is achieved without appreciable increase of the film's density, which especially for certain applications, e.g. paper coating, can be an important advantage. The maximum acceptable vesicle diameter will now probably depend on the average diameter of the vesicular granule, but it has been found that the opacity effect is dependent on the diameter of the individual vesicles, as the optimal refractive effect of vesicles containing air is achieved in the range of approx. 0.2 to 0.5 micron diameter.

It is an important feature of this embodiment of the present invention that when the vesicular polymer granules are suitably sized, they can be used to impart opacity to a clear paint film without reducing its surface gloss, which is typical for granule diameters below 1 micron. On the other hand, by choosing slightly coarser granules, both the opacity and the surface gloss can be regulated in a predetermined manner, as the coarser the granules, the lower the gloss that can be achieved.

As the granulate and the film-forming polymer can have different physical properties, the granulate can also be used to adjust the overall mechanical properties of a film in which the granulate is incorporated. The use of, for example, relatively strongly cross-linked vesicular granules produced according to the invention will result in an increase in the film's hardness and wear resistance.

The paints can be produced by vesicular stirring

granules into a common paint composition consisting of a film-forming polymer and optional pigment, typically to a maximum granule volume concentration of 55% based on the paint's total solids content in gloss and semi-gloss paint, while for matte paint the granule volume concentration can be as high as 95%.

The invention is illustrated by the following examples,

where all parts express weight.

Example 1

Preparation of vesicular polymer granules from a

unsaturated polyester resin selected as described above.

An unsaturated polyester resin was prepared conventionally

method from fumaric acid, phthalic anhydride and propylene glycol in a molar ratio of 3:1:4. The product had an acid number of 44 mg KOH/g and a Gardner Holdt viscosity of T as a 70% by weight solution in xylene.

The suitability of the resin for the production of vesicular granules was confirmed by adding 5% by weight of aqueous ammonia to a stirred portion of a 60% solution of the resin in xylene,

the ammonia being present in a molar equivalent amount calculated on the resin's free carboxyl groups. A stable water-in-oil dispersion was formed in which the dispersed droplets of aqueous liquid were substantially less than 5 microns in diameter.

A solution of 18.0 parts unsaturated polyester resin

and 0.5 part benzoyl peroxide in 12.0 parts styrene was added with rapid stirring to an aqueous liquid consisting of 4.06 parts hydroxyethyl cellulose, 7.28 parts polyvinyl alcohol with molecular

weight approx. 110,000 and 20% residual vinyl acetate units, 719.0

parts water and 2.0 parts diethylenetriamine. A suspension of spheres of polyester resin solution with an average diameter of 15

micron was formed, the spheres containing numerous small dispersed droplets of aqueous liquid. The beads were polymerized by heating the suspension in a closed vessel at 95°C for three hours. The suspension of the granules thus formed was diluted with 4000 parts of water,

was allowed to stand for a day and the concentrated suspension of settled granules was separated from the bulk of the water. The average granule diameter was 15 microns and by microscopic examination it was estimated that the granules contained 25% by volume of vesicles with a diameter of less than 2 microns. The granulate was allowed to air dry, and substantially air-filled vesicles formed.

Example 2

This example illustrates the effectiveness of select-

the sample to avoid the use of unsatisfactory polyester resins for the practice of the invention.

Two unsaturated polyester resins were prepared from the reactants used in Example 1, one having an acid number of 25 mg KOH/g and a Gardner H<p>ldt viscosity of X as a 70% by weight solution in xylene, and the other had an acid number of 8 5 mg KOH/g and viscosity K with the same percentage of solids.

When the selection sample with aqueous ammonia as described

in Example 1, was performed on the two resins, the first was found to contain dispersed small droplets of aqueous liquid substantially below 5 microns in diameter while the second resin gave an unstable dispersion with a much larger droplet diameter.

The two resins were converted into granules by the method described in example 1, the first resin giving granules with an average diameter of 15 microns and containing

containing 10% by volume of vesicles less than 2 microns in diameter.

The second resin gave granules with an average diameter of approx.

5 microns, but without vesicles having formed therein. The second resin's unsuitability for practicing the invention was consistent with the results of the selection test.

Example 3

In this example, the effect of base concentration on the granules' vesicle content is illustrated.

Four portions, each of 15.0 parts of an 80 weight percent solution of the unsaturated polyester resin of Example 1

in styrene to which 0.5 part benzoyl peroxide had been added, was

each separately dispersed in the following aqueous liquids <p>g poly-

characterized by the general procedure indicated in example 1:

In each case, the suspended resin solution beads were polymerized into granules with an average diameter of 15 microns and containing vesicles of approx. 2 micron diameter.

The concentration of the vesicles in the granules increased with

increasing concentration of base to a maximum in sample no. 3, but was unaffected by further addition of base.

Example 4

This example relates to the production of vesicular polymer granules using an inorganic base.

An unsaturated polyester resin was produced with

an acid number of 38 mg KOH/g and a Gardner Holdt viscosity of W as a 70% by weight solution in styrene from maleic anhydride, phthalic anhydride and propylene glycol in a molar ratio of 1:1:2. When the resin was subjected to the above-described selection test, it formed dispersed aqueous droplets less than 5 microns in diameter.

By the general method described in the example

1, vesicular granules were prepared from 30.0 parts of the above resin solution in styrene to which were added 3.0 parts of toluene and 0.5 part of benzoyl peroxide, dispersed as small drops in an aqueous liquid consisting of:

The granules had a diameter frj| 1-3 microns and contained 20 volume percent vesicles with a diameter of 0f05-0.5 microns.

Example 5

This example relates to the production of vesicular polymer granules using a mixed base.

An unsaturated polyester resin with an acid number of 40 mg KOH/g and a Gardner Holdt viscosity of Z was prepared as a 70% by weight solution in styrene from fumaric acid, phthalic anhydride and propylene glycol in a molar ratio of 3:1:4. When the resin was subjected to the selection test described above, it formed dispersed small droplets less than 5 microns in diameter.

By the general method described in example 1, vesicular granules were prepared from 53.5 parts of the above-mentioned resin solution in styrene to which were added 21.5 parts of styrene and 1.0 part of benzoyl peroxide dispersed as small drops in an aqueous liquid consisting of:

The granules had an average diameter of 5 microns and contained 30 volume percent vesicles with a maximum diameter of 2 microns.

Example 6

This example relates to the production of vesicular polymer granules using a mixture of polymerizable monomers for co-reaction with the unsaturated polyester resin.

An unsaturated polyester resin with an acid number of 33 mg KOH/g and a Gardner Holdt viscosity of W was prepared as a 70% by weight solution in styrene from maleic anhydride, phthalic anhydride propylene glycol in a molar ratio of 1:1:2. When the resin was subjected to the selection test described above, it formed dispersed small droplets substantially less than 5 microns in diameter.

By the general procedure described in example 1, vesicular granules were prepared from 37.4 parts of the above-mentioned resin dissolved in 33.0 parts of vinyltoluene and 4.5 parts of methyl methacrylate to which 2.0 parts of benzoyl peroxide were added, after which the solution was dispersed as spheres in a watery liquid consisting of:

An additional 175.0 parts of water was added to the suspension before heating to 95°C to polymerize the resin components.

The vesicular granules had an average diameter of 15 microns and contained 30 volume percent vesicles with diameters below 2 microns.

Example 7

This example concerns the production of latex paints containing vesicular granules produced by the method according to the invention.

A series of aqueous latex paints were prepared by the following general procedure using vesicular granules as indicated below.

A mixture of. 12.1 parts rutile titanium dioxide pigment and 0.06 part sodium hexametaphosphate were added to 80.0 parts aqueous slurry of vesicular polymer granules containing 14.0 weight percent granules and stirred with a high speed disk mixer for 30 minutes. The stirring rate was then reduced to reduce aeration of the mixture and 17.2 parts 46.5% by weight commercial aqueous acrylic copolymer latex was added. The granules used in each of the paint samples thus prepared were as follows:

Films of each paint were brush applied to glass-

and 2

plates with a spread of approx. 12 m per liter and allowed to dry in air at 25°C and 50% relative humidity. All the paints formed continuous, dry films in less than an hour. Paint (f) formed a glossy film and paint (g) a semi-gloss film. The other paints formed films with lower gloss levels, they were even, matte films. It was observed that the films from samples (b) and (c) had lower opacity than the other films, which was consistent with the lower vesicle content in the granules contained therein. However, their opacity was higher than that of the films formed from control paints having the same overall composition as the test paints, but in which the vesicular granules were replaced by non-vesicular polymer granules whose granules had approximately the same diameters.

Example 8

This example concerns the production of non-aqueous paints containing vesicular polymer granules produced by the method according to the invention.

Two paint mixtures were prepared as follows

general procedure using granules prepared as indicated in examples 4 and 5 respectively.

Rutile titanium dioxide was dispersed to a pigment volume concentration (on solids) of 12% in a solution of 98/2 methacrylate/methacrylic acid copolymer solution (20.0 parts 40% solution)

in a 1:1 mixture of toluene and acetone. Dry vesicular polymer granules (5.0 parts), acetone (10.0 parts), toluene (10.0 parts) and n-butyl benzyl phthalate (5.0 parts) were added to the dispersion and the aggregates dispersed by stirring under high speed with sand .

After removing the sand, the paint mixtures were

sprayed onto Morest strips, and after drying at room temperature for one hour, the coated strips were baked in at 150°C for 30 minutes.

Each test provided a smooth, satin film.

The films were compared with films of control paint prepared

and tested in the same way, but where the vesicular granules were replaced with an equal volume of granules of the same size and composition, but free of vesicles. In each case, the films containing vesicular granules had a higher opacity than the control films.

Example 9

This example concerns the production of a polymer sheet containing vesicular granules produced according to the invention.

Polyethylene granules (98.0 parts) were mixed with 2.0 parts of dry, vesicular polymer granules prepared according to Example 5. The dry mixture was extruded in the form of a tube, fed through a granulator and then extruded in the form of a sheet of about. 1 mm thickness. The sheet was opaque, whereas a sheet formed in the same way from polyethylene granules without vesicular polyester granules was transparent.

Example 10

This example concerns the production of vesicular polyester resin granules where the polyester resin was pigmented

with titanium dioxide.

An unsaturated polyester resin was prepared conventionally

manner from fumaric acid, phthalic anhydride and propylene glycol in molar ratio

about. 3:1:4. The product had an acid number of 22.5 mg KOH/g and a Gardner Holdt viscosity of Z2 as a 70 percent solution in styrene. In the selection test described in example 1, it formed

aqueous small droplets less than 5 microns in diameter were dispersed in the resin solution.

To 128 parts of a 40 weight percent solution of the resin in styrene was added 32 parts of rutile titanium dioxide pigment and the mixture was mixed for 30 minutes using a high-speed mechanical stirrer.

A mixture of 3 parts cumene hydroperoxide and 1 part surfactant (octylphenol/ethylene oxide cocondenate containing 5 ethylene oxide units per molecule) was rapidly stirred in the above-mentioned stirrer, and the mixture was thereby instantly suspended in spherical form in an aqueous continuous phase by the general method described in example 1, the continuous phase consisting of the following mixture:

Balls of resin solution with a largest diameter of 25 microns and containing dispersed aqueous droplets formed in the continuous phase. An additional 120 parts water and 1.0 part 0.880 ammonia were then added to the suspension. Cross-linking of the unsaturated polyester resin was then carried out by heating the above suspension to 95°C and holding it at this temperature for 1 hour.

The cross-linked granules had a mesh diameter of approx. 25 microns and contained 25 volume percent vesicles with a maximum diameter of 1 micron.

Example 11

This example relates to the production of vesicular polyester resin granules in which the vesicles contained titanium dioxide pigment.

An aqueous pigment dispersion was prepared by sandblasting the following mixture:

The above dispersion was added under vigorous mechanical stirring to 128.0 parts of a 40% by weight solution in styrene of the unsaturated polyester resin of Example 10 in which it formed a water-in-oil type dispersion of aqueous droplets. To this mixture was then added 3.0 parts of kurnen hydroperoxide, and the entire mixture was then added with stirring to an aqueous continuous phase where it formed a suspension of discrete spheres, each of which contained dispersed droplets of aqueous liquid. An additional 318 parts water and 1.0 part 0.880 ammonia were then added.

The composition of the aqueous continuous phase

was as follows:

The unsaturated polyester resin polymerized on standing at room temperature for 24 hours and gave cross-linked vesicular granules where the granules had diameters up to 30 microns. A sample of the granulate was filtered from the suspension and dried in air. A cross-linked cross-section of granules seen under an electron microscope showed the presence of an internal vesicular structure and the presence of the pigment particles inside the vesicles. the vesicle volume was assessed to be 30% of the total granule volume.

Example 12

This example relates to the production of vesicular polyester resin granules containing gaseous vesicles.

An unsaturated polyester resin was produced in the usual way from fumaric acid, phthalic anhydride and propylene glycol in a molar ratio of approx. 3:1:4. The product had an acid value of 38 mg KOH/g and a Gardner Holdt viscosity of Z2 as a 70 weight percent solution in styrene. The resin passed the selection test described above.

To 32.0 parts of a 40 weight percent solution in styrene of the above resin was added 0.2 part octylphenol/ethylene oxide surfactant (such as Example 10) and 0.7 part cumene hydroperoxide.

The above mixture was added with stirring to an aqueous continuous phase in which it formed separate globules containing dispersed aqueous droplets. The composition of the continuous phase was as follows:

A further 130 parts of water were then added.

The suspended beads of unsaturated polyester resin solution were crosslinked by keeping the suspension at 90°C for 2 hours. The suspension of cross-linked vesicular granules was then dried by

passing it through a standard spray dryer yielding dry (less than 2% moisture by weight) vesicular granules of maximum diameter of 10 microns.

Example 13

This example concerns the effect of polyamines on vesicle size in crosslinked polyester resin granules.

An aqueous continuous phase was prepared by mixing:

An unsaturated polyester resin was then prepared in the usual manner from fumaric acid, phthalic anhydride and propylene glycol in an approximate molar ratio of 3:1:4. The product had an acid number of 40 mg KOH/g and a Gardner Holdt viscosity of Z2 as a 70 weight percent solution in styrene.

To 75 parts of a 50% by weight solution in styrene of the above-mentioned polyester resin were added 2 parts of a 55% by weight paste of benzoyl peroxide in n-butyl benzyl phthalate. The mixture was then added with stirring to the above-mentioned aqueous continuous phase in which it formed globules of resin solution in which dispersed aqueous particles could be seen. An additional 100 parts of water was then added to the mixture and the polymerization accelerated by heating the mixture to 90°C for 2 hours.

The cross-linked vesicular polymer granules thus formed had a maximum diameter of 30 microns with vesicles of submicron size.

The above experiment was repeated omitting diethylenetriamine. Vesicular granules of similar size were produced, but the vesicles were 1-5 microns in diameter, illustrating the importance of the polyamine in providing small vesicles.

When paints were prepared from each granule sample by the general method of Example 1, it was found that dried films of the paints containing granules in which the vesicles were of submicron size had a higher opacity than films of paint containing coarser vesicular granules.

Example 14

This example relates to the production of vesicular polyester resin granules.

An aqueous continuous phase was prepared from:

by stirring the above ingredients together for 2 hours.

The hydroxyethyl cellulose was of the same quality as

used in previous examples and had a viscosity of approx. 20,000

as a 1% by weight solution in water at 25°C.

A polyester resin was prepared in the usual manner from isophthalic acid, fumaric acid and propylene glycol in an approximate molar ratio of 1:2:3. The product had an acid number of 37 mg KOH/g and a Gardner Holdt viscosity of U as a 70% by weight solution in styrene. The resin passed the selection test when tested as a solution

in xylene.

A mixture of 75 parts of a 50% solution in styrene of the above resin and 2 parts of a 55% paste by weight of benzoyl peroxide in n-butyl benzyl phthalate was stirred into the above continuous aqueous phase in which it formed a stable suspension of spheres with a maximum diameter of 30 microns , <y>further 100 parts of water were added and the droplets polymerized by heating to 90°C for 2 hours.

The vesicular cross-linked granules thus formed had diameters of a maximum of 28 microns.

Example 15

• This example concerns the effect of the polymerizable monomer composition on granules produced by the method according to the invention.

The general procedure of Example 14 was followed using an unsaturated polyester resin of maleic anhydride, phthalic anhydride and propylene glycol (molar ratio about 1:1:2) having an acid number of 39 mg KOH/g and a Gardner Holdt viscosity of W as a 70 weight percent solution in styrene. Also, the polymerizable monomer (styrene) in that example was replaced with the following monomers i

a series of experiments:

(a) divinylbenzene

(b) vinyl toluene/methyl methacrylate (weight ratio 4:1)

(c) athyrene/divinylbenzene (weight ratio 95:5)

(d) methyl methacrylate

(e) vinyl acetate

The monomers a-c gave satisfactory vesicular cross-linked polyester granules, while the monomers d and e, on the other hand, gave granules with a low vesicle content and a high content of non-vesicular granules. It should be noted that both methyl methacrylate and vinyl acetate are relatively water-soluble compared to other monomers and do not fall within the current understanding of virtually water-insoluble polymerizable monomers.

Example 16

This example relates to the production of vesicular polyester granules from a similar unsaturated polyester resin as that of example 3, but with a higher viscosity.

An unsaturated polyester resin was produced by

the general method in example 4, but where the 40 percent by weight propylene glycol in said example was replaced with ethylene glycol. The resin had an acid number of 35 mg KOH/g and a Gardner viscosity of Z2 as a 70 weight percent solution in styrene. By the general method in example 4, vesicular polyester resin granules were produced from this resin. The granules were somewhat larger than those in example 4, as they had a maximum diameter of approx. 20 microns and contained vesicles with diameters from 1 to 5 microns.

Example 17

This example concerns the effect of the base type on the method according to the invention.

A continuous aqueous phase was prepared by mixing the following materials for 2 hours:

A further series of aqueous phases was prepared according to the above general recipe, but in which the triethyleneamine was replaced by the bases indicated in the table below on a chemically equivalent basis.

A polyester resin was prepared in the usual manner from maleic anhydride, phthalic anhydride and propylene glycol in an approximate irole ratio of 1:1:2. The product had an acid value of 38 mg KOH/g and a Gardner Holdt viscosity of W as a 70% by weight solution in styrene.

A mixture of 30 parts of a 60 percent by weight

solution in styrene of the above resin and 1 part of a 55% by weight paste of benzoyl peroxide in n-butyl benzyl phthalate were then added with stirring to each of the above aqueous phases and the polymerization initiated by heating the mixtures to 90°C for 2 hours with those shown below results.

The results showed that unsatisfactory results were obtained with bases having a dissociation exponent greater than 8, while the best results were obtained when the base had a dissociation exponent within the preferred range of less than 5.

Example 18

This example concerns the effect of the base concentration on the method according to the invention.

In the general method in example 17, an attempt was made to produce vesicular granules of cross-linked polyester resin from a polyester resin. prepared from fumaric acid, phthalic acid and propylene glycol in an approximate molar ratio of 3:1:4. The resin had an acid value of 25 mg KOH/g and a Gardner Holdt viscosity of X<+> as a 70 weight percent solution in styrene. The resin passed the standard selection test as a solution in xylene.

The base used was diethylenetriamine, and the concentration expressed as equivalents of base per equivalents of carboxyl groups in the resin were as shown for each of the three trials.

The results showed that when the concentration limit of base according to the invention was exceeded, the result was unsatisfactory. When the base level fell within the preferred range, excellent results were obtained in the experiment at a base level of 4:1.

Example 19

This example concerns the effect of the viscosity of the unsaturated polyester resin on the method according to the invention.

An unsaturated resin was prepared from fumaric acid, phthalic anhydride and propylene glycol in a molar ratio of approx. 3:1:4. The product had an acid number of 43 and a Gardner Holdt viscosity of K as a 70 weight percent solution in xylene.

A mixture of 15 parts of a 70% by weight solution of the above resin in styrene and 0.5 part of a 55% by weight paste of benzoyl peroxide in n-butyl phthalate was used to prepare vesicular polyester resin granules by the general procedure of Example 17 using the following continuous aqueous phase:

Granules of up to 30 microns in diameter were formed, but it was observed that some of these were not vesicular. That is to say, the use of an unsaturated polyester resin with a lower viscosity than the limit preferred according to the invention gave a lower yield of vesicular granules than the theoretical.

Example 20

This example relates to the effect of the unsaturated polyester resin's acid number on the process according to the invention.

The polyester resin of Example 19 was further condensed to give a product with a Gardner Holdt viscosity of Z2 as a 70 weight percent solution in styrene. The acid number of the resin dropped to 4 mg KOH/g.

Example 19 was then repeated using the above-mentioned resin instead of the resin in Example 19. Cross-linked polyester resin granules with diameters up to 40 microns were formed, but the degree of vesiculation was found to be exceptionally low when compared with, for example, the granules in Example 1. A sample of granules was dried in air while providing gas-containing vesicles and processed into a paint by the general procedure of Example 7. A dry paint film containing this granule when tested as indicated in Example 7 showed only a slight increase in opacity compared to the control sample where non-vesicular granules had been used.

It will be seen from this that increasing the viscosity of the unsaturated polyester resin in Example 19 so that it remained within the preferred limits, for one reason or another did not give the formed granules the preferred vesicular structure when the viscosity increase was accompanied by a drop in the acid number to below the lower preferred limit.

Example 21

This example concerns the production of large vesicular cross-linked polyester granules.

A mixture of:

was stirred for 1 hour forming a continuous aqueous phase. The following ingredients were stirred to homogeneity with a high-speed mixer:

An unsaturated polyester resin was prepared in the usual way from fumaric acid, phthalic anhydride and propylene glycol in a molar ratio of approx. 3:2:1. The resin had an acid number of 22 mg KOH/g and a Gardner Holdt viscosity of Z-2 as a 70 weight percent solution in styrene.

A solution of 72.5 parts of the above resin i

55.5 parts of styrene were prepared and to this was added 1 part of a surface-active agent, namely the ethylene oxide cocondensate used in example 10. To this mixture, while stirring, was slowly added the above-mentioned pigment dispersion which formed separate dispersed particles in the resin solution, after which was added 3 .0 parts kurnen hydroperoxide. The dispersion thus prepared was then immediately added with stirring to the continuous aqueous phase in which it formed a suspension of spheres, the batch was then held at 95°C for 1h hours for polymerization of the spheres which formed cross-linked vesicular polyester resin granules with a maximum diameter of 0, 5 mm.

Claims (5)

1. Process for the production of a vesicular, cross-linked polyester resin granulate, in which a solution in a substantially water-insoluble, polymerizable, unsaturated monomer of an unsaturated polyester resin is suspended as discrete spheres in an aqueous, continuous phase, and polymerization is initiated to cross-link the the polyester resin and formation of granules, characterized in that an unsaturated polyester resin is used which contains carboxyl groups and which is soluble in xylene in the proportion by weight in which it is to be used in the process as a solution in the unsaturated monomer, and in that when 5% by weight of a aqueous ammonia solution where the ammonia content is 1 molar equivalent based on the acid number of the resin is stirred into the aforementioned xylene solution of the polyester resin, then a dispersion of aqueous, liquid small droplets essentially less than 3 µm in diameter is formed spontaneously in this, the dispersion remains stable for at least 30 minutes, wherein unsaturated polyester resin is suspended in d an aqueous continuous phase in the presence of from 0.3 to 10.0 equivalents per carboxyl group of a base that has a dissociation exponent of less than 8, and further that the vesicles form spontaneously inside the droplets. 2. Method as stated in claim 1, characterized in that small drops of an aqueous liquid are predispersed in the solution of the unsaturated polyester resin before the resin is suspended in the continuous aqueous phase. 3. Method as stated in claims 1-2, characterized in that a base is used which has a dissociation exponent less than 5. 4. Method as specified in claims 1-3, characterized in that from 0.7 to 3.0 equivalents of base are used per carboxyl group. 5. Method as stated in claims 1-4, characterized in that an unsaturated polyester resin is used which has an acid number of 10-50 mg KOH/g.