GB1599593A

GB1599593A - Expanded styrene-polymers and polyolefin micro-bits and their preparation

Info

Publication number: GB1599593A
Application number: GB2148/78A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-09-15
Filing date: 1978-01-19
Publication date: 1981-10-07
Also published as: SE7800560L; IL53773A; FI780163A; BR7800233A; ATA28578A; JPS5497667A; AU3238078A; FR2403355B1; DE2801905A1; CA1093749A; DK11478A; ZA78144B; IT1105257B; FR2403355A1; JPS637925B2; NO780088L; CH649737A5; SE439490B; MX147706A; IL53773A0

Abstract

An expanded thermoplastic is described which comprises styrene polymers and specific polyolefins and is present in the form of microparticles which have specific longitudinal and lateral dimensions and are free of intact cells of the expanded plastic particles from which they were obtained, the individual microparticles being non-uniform in shape and their density being between approximately 85% and 100% of the density of the plastic before expansion. A process for producing the plastic particles is also described.

Description

(54) EXPANDED STYRENE-POLYMERS AND POLYOLEFIN MICRO-BITS AND THEIR PREPARATION (71) I, MAX KLEIN, of 257 Riveredge Road, Tinton Falls, New Jersey 07724, in the United States of America, a citizen of the United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention is that of (a) micro-bits of an expanded thermoplastic polymer which is nonbrittle in its expanded form and selected from a styrene-polymer, a polyethylene, polypropylene, a polybutene, and a poly-methylpentene, and (b) a method for preparing these micro-bits from bit-pieces of the respective styrene-polymer (as hereinafter defined) or polyolefin (as hereinafter defined) from polyethylene to the polymethylpentene.

These micro-bits, which briefly may be called expanded styrene-polymer or expanded polyolefin micro-bits, of the invention (i) range in size from 325 microns in length and also from the same in width down to 40 microns in length and to 20 microns in width, (ii) have a specific gravity of from 85 percent, to the same as that, of the starting polymer which was expanded and then disintegrated into the micro-bits; (ili) are substantially completely to entirely completely free of intact cells of the expanded polymer from which they were produced and (iv) their particles lack uniformity in outline.

Viewed (a) at a magnification of, for example, 161 times (by transmitted light, in Figure 1 below) they appear as clusters of randomly arrayed fibers, and (b) under a scanning electron microscope (abbreviated SEM) at magnifications of 360 and 380 times (in Figures 4 and 13) they appear much like irregular separate pieces of writing paper that were individually compressed coarsely in the hand and then allowed to rebound to the extent possible from the resilient after releasing the pressure by opening the hand.

Further SEM examination at other magnifications as at (i) 1800 times (in Figure 3 below) of part of the same location as in Figure 4 shows formations of what appear to be extended apart and distorted outlines of ruptured boundaries of what before being ruptured was an expanded honeycomb array of hexagonal and pentagonal cross sections of cells, (ii) 4000 times (in Figure 2) shows them to appear much like that of randomly spread apart and partially overlapping not quite fully open rose petals.

Other SEM magnifications ranging from 500 to 5000 times show the micro-bits to resemble minute coral formations (as in at least Figures 7 to 9), in wavelike appearance (magnified 1000 times as in Figure 10), and in somewhat ruffled fluted formation (magnified 10,000 times, Figures 11 and 14, and 20,000 times, Figures 12 and 15).

The expression "styrene-polymer" means polystyrene itself and thermoplastic polymers of any polymerizable substituted styrenes as well as copolymers of styrene with one or more other compatible polymerizable substances as the nuclear-alkylated or -halogenated styrenes such as the ring-methyl or -chlorine-substituted styrenes, or even alpha-methyl styrene, or with beta-unsaturated esters, ethers, amides, or nitriles of acrylic acid and their alpha-positionalkylted homologs, vinyl esters of aliphatic and aromatic carboxylic acids, N-vinyl compounds of N-vinylcarbazole, N-vinyl-imidazole or N-vinylpyrrolidone.

Such thermoplastic copolymers of styrene usually should contain at least 50% of styrene by weight, or it may be the predominating component or at least equal in predominance to any other higher present component of any terpolymers. The copolymers of styrene include also any of the various impact polystyrene containing a major part of styrene and a minor part of a styrene-butadiene rubber (usually designated SBR, sometimes called Buna-S), for example, as produced by emulsion polymerization of about 75 parts of butadiene and about 25 parts of styrene. Thus, styrene-polymers also include styrene alloys (i.e. pressure or melt mixtures) of polystyrene with other compatible polymers generally of ethylenically unsaturated monomers.

The term "polyolefin" as used herein means a homopolymer of an olefin from ethylene to methylpentene, thereby embracing polyolefins of the group from a polyethylene and a polypropylene to a poly-methylpentene and also a copolymer of polypropylene with from about 20 to 30 percent of polyethylene by weight, and a melt alloy of polypropylene with a co polymer of polyethylene with up to 30% of said copolymer by weight being polyvinyl acetate, and said polypropylene exceeding by weight at least 50% of said melt alloy; and as to the polyethylene embracing the high molecular weight, (at least 6000) product and is generic as embracing low density polyethylene (specific gravity below 0.92), the high density product (sp. g. over 0.94, generally 0.941 to 0.965), and the medium density polymer product (a blend of both the high and low), as well as the impregnatable polyethylene (e.g. an extruded melt mix of polyethylene with 10% polystyrene and which can be called "polyethylene-polystyrene alloy"); all of which are available in flake or in cubes similar to polystyrene pellets.

The term "bit-pieces" includes any of the discrete free-flowing forms of any of the styrene-polymers and of any of the polyolefins from polyethylene to the poly-methylpentene, such as the various sizes of granules made by cutting the respective extruded polymer into small lengths usually called pellets or crystal (as with a styrene-polymer) or pellets or cubes of a polyethylene-polystyrene alloy, the various sizes of styrene-polymer beads obtained from suspension polymerization or otherwise as by molding the particles obtained by disintegrating any of these different polymer forms, and the so-called "grind" including the coarsely ground molded polymer or waste or other scrap such polymer (of various sizes, e.g., 1/8 inch thickness, 1/4 inch width, and 3/8 inch length), and any other small sized shapes of any of them.

Expandable styrene-polymer bit-pieces can be prepared by suitable known methods, for example, preparing expandable styrene-polymer bit-pieces as disclosed in U.S. Patent No.

2,983,692 issued May 9, 1961. Expandable polyethylene-styrene alloy can be prepared similarly.

Expanded styrene-polymer bit-pieces can be prepared from expandable polystyrene by suitable known methods. One method for preparing expanded styrene-polymer bit-pieces is by heating them, for example, with air or steam is disclosed in U.S. Patent No. 2 983 692 (column 4 lines 65-69), "to a temperature above the softening point of the styrene polymer" as disclosed in U.S. Patent No.3 001 954 (column 3 lines 30-23). See also U.S. Patent No. 3 159 594 (column 2 lines 24-27). Expanded polyethylene-polystyrene alloy bitpieces can be prepared similarly.

Expanded bit-pieces of the polyethylene, polypropylene, polybutene or poly-methylpentene can be produced by preparing the respective expanded polyolefin by suitable known methods including incorporating into the specific polyolefin (before extruding it) a chemical foaming agent (so-called pneumatogen, usually a complex nitorgen-containing organic compound that decomposes at the extrusion temperature, liberating nitrogen) with extrusion temperature adjusted so that the pneumatogen decomposes as the polyolefin leaves the outlet of the extrusion die, as briefly described in Plastics Extrusion Technology, by Allan L. Griff Reinhold Publishing Corp., New York, N.Y.

(1968) page 221, and reducing the expanded polyolefins into bit-pieces by cutting or otherwise.

Certain physical features of the micro-bits of the invention are shown by the photomicrographs of the dry micro-bits in the first fifteen figures of the accompanying drawings, of which Figures 1 to 9, 14 and 15 are of polystyrene micro-bits and Figures 10 to 13 are of low density polyethylene micro-bits, and wherein Figure 1 is a photomicrograph at a magnification of 161 times, by transmitted light; Figure 2 is a SEM photomicrograph of the micro-bits at magnification of 4,000 times; Figure 3 is a SEM microphotograph at magnification of 1,800 times of about the area that gave the lower left quarter seen in Figure 4; Figure 4 is a SEM microphotograph taken at magnification of 360 times; Figure 5 is a microphotograph taken at a magnification of 100 times; Figure 6 is a SEM microphotograph taken at magnification of 500 times of the area that gave the delineated center portion of Figure 5; Figure 7 is a SEM photomicrograph at 1,000 times magnification of the area that gave the delineated portion of Figure 6; Figure 8 is a SEM photomicrograph at magnification of 2,000 times of the area that gave the prominent right portion of Figure 7; Figure 9 is a SEM photomicrograph taken at magnification of 5,000 times and shows the area that appeared in the lower right hand quarter of Figure 8; Figure 10 is a SEM photomicrograph taken at magnification of 1,000 times of polyethylene micro-bits and apparently of the location that gave the area in the lower left hand quarter of the upper right hand quarter of Figure 13; Figure 11 is a SEM photomicrograph taken at magnification of 10,000 times and embracing the area of the slide seen in about the center of Figure 10; Figure 12 is a SEM photomicrograph taken at magnification of 20,000 times and covering the area of the slide seen in lower magnification in about the middle of Figure 11; Figure 13 is a SEM photomicrograph taken at magnification of 380 times of the same polyethylene micro-bits involved in Figures 10 to 12; Figure 14 is a SEM photomicrograph taken at magnification of 10,000 times of polystyrene micro-bits; and Figure 15 is a SEM photomicrograph at magnification of 20,000 times of a portion of the polystyrene micro-bits slide viewed in Figure 14.

Figure 16 is a schematic illustration of a system for removing the trapped water from the micro-bits of the invention as obtained in the aqueous slurry leaving the comminutor wherein the micro-bits are produced from the expanded starting polymer (as more fully described shortly after Example 2 below).

The expanded micro-bits of the invention are prepared by continuously feeding expanded bitpieces of a styrene-polymer or any of the aforesaid polyolefins and water into a confined comminuting zone, having a feed inlet to it, re repeatedly impelling the resulting mixture of the starting bit-pieces in the water through a circular path by repeated impact on them in the water by a plurality of impact surfaces spaced apart from one another and rotated around the axis of said circular path at from 4,700 to 8,000 revolutions per minute, and at the same time by said impact surfaces driving said expanded bit-pieces to and against corner-shaped edges of a dispersed plurality of from orifices which may be (a) substantially circular and having a diameter of from 0.102 to 3.175 millimeters (i.e. mm.) or may be non-circular having a minor dimension of from 0.254 to 3.175 mm. and a major dimension of from 3.81 to 12.7 mm., and (b) being arranged in screening array in an arcuate plane spaced radially out of range of said impact surfaces to an extent that need be only sufficient to avoid collision between said orifices and said impact surfaces, e.g. from 0.508 to 1.016 mm., and thereby repeatedly tearing, ripping and shearing micro-bits of the respective expanded polymer from said bit-pieces thereof; said fed in water being so proportioned to said fed in expanded polymer bit-pieces to prevent the content of the comminuting zone from reaching a temperature that would adversely effect the integrity of said starting bit-pieces and/or the desired micro-bits.

The preparation of these micro-bits of a styrene-polymer or of a polyolefin (from a polyethylene to a poly-methylpentene), and so also the method of the invention, can be conducted by disintegrating the respective starting expanded styrene-polymer or polyolefin bit-pieces in a comminuting machine (such as that produced by Fitzpatrick Company, of 832 Industrial Drive, Elmhurst, Illinois 60126, U.S.A.), according to their Bulletin No. 152 copyright 1968) using the broached fixed blades (identified therein by "Code DS-225") to replace the blades or other comminuting elements, mounted for rotation in the comminuting chamber model DAS06, both shown on that bulletin's page 5. That chamber is liquid-tightly capped, for example, by a cover such as shown in their Code M44D6 or Code MA44D6 (upper half of page 3 of their Bulletin 152).

That model DAS06 comminuting chamber is rectangular in horizontal cross-section and has a pair of opposed parallel entirely vertical walls integrally joined at each of their opposite ends by a separate one of a pair of opposed vertically arcuate walls each with its convex face exposed to the exterior.

Sixteen identical, slat-shaped comminuting arms are separately removably but fixedly carried with their snugly adjacent to one another bases encircled about, and keyed to, the operating shaft and intermediate its free outer mounting ends. These arms extend radially out from the shaft (e.g. 127 mm from its axis to the outer end of each arm) with the first of each consecutive four of them extending horizontally toward one arcuate wall, the second of each four extending vertically, the third four of them extending toward the other arcuate wall, and the fourth four of them extend ing vertically downward.

Each arm is rectangular in cross-section in a plane running through the entire length of the shaft's axis and of that arm, and of each arm 180 removed from it. The outer end of each arm meets at right angles with its two wider sides (25.4 mm. width) and its narrow or impact side (9.525 mm. wide) facing the direction of rotation. That narrow side also meets at right angles with the two wider sides which are parallel to one another for most of their width and with the trailing third of their surfaces tapering to one another and terminating in a knife edge of their trailing end.

Each free exposed end of the shaft extends through its respective stuffing box in its neighboring one of the two parallel vertical walls on through a bearing carried on a respective trunnion affixed to the machine's foundation and spaced outwardly away from the respective wall. A driving pulley is mounted on each end of the shaft extending outwardly from its respective mounting trunnion.

The bottom of the comminuting chamber is an exchangeable dish-shaped, arcuate screen curved convexly downward with an inside radius (from the axis of the operating shaft) equal to the length of a comminuting arm plus 0.762 mm. clearance). The screen's overall rectangular peripheral opening has such dimensions and shape to enable it to be removably fitted in a liquid-tight engagement with the bottom of the four walls of the comminuting chamber.

The screen has staggered rows of, for example, circular holes varying in diameter as from 0.102 to 3.175 mm. and closely spaced to one another with sufficient space between them for the screen to hold up under working conditions.

Except for its starting material feed hopper inlet at one side of it, the rest of the chambers cover is arcuate and convex upwardly with a radius (from the axis of the operating shaft) sufficient for the rotating arms to have a 0.762 mm. clearance from the inwardly facing surfaces of a plurality (e.g. three) pre-breaker bars (about 20.32 cm. long and 6.35 mm. wide) protruding for 3.175 mm. along their entire length into the interior of the comminuting chamber, and extending spaced apart from one another and parrallel to the axis of the operating shaft.

The selected driving pulley on the operating shaft is connected by driving belts extending from a motor shaft drive pulley and can be operated at speeds embracing the range of from 4,700 to 8,000 r.p.m., and more effectively from 5,000 to 7,500 r.p.m.

The micro-bits of the invention are variously applicable, for example, in filtering and improving fluids, both liquid and gaseous. This is done, for example, by admixing the selected styrene-polymer or polyolefin micro-bits into the liquid to be improved and thereafter filtering them out, or by filtering the liquid to be improved through a bed of the micro-bits. The polymer micro-bits thereby remove invisible dissolved or invisibly suspended organic material from the liquid and ordinarily leave it free from development thereof even after long standing.

To illustrate, tap water in Matawan, New Jersey, U.S.A., was filtered through a Whatman No. 2 filter paper ("Whatman" is a Registered Trade Mark) to the extent of 473.2 cubic centimeters (i.e. cc.) into a first clean, 946.3 cc.

Mason jar which then was tightly sealed.) 0.4 grams of the micro-bits (prepared from expanded polystyrene bit-pieces) were wetted with about 20 cc. of this same tap water and admixed with about 473.2 cc. of the tap water and then filtered through another Whatman No. 2 filter paper into a similar second clean, 946.33 Mason jar and tightly sealed.

A week later a slight yellow haze was noted in the first jar, but the water (which had been admixed with the micro-bits) in the second jar still was perfectly clear. The yellow haze in the first jar increased in amount and in density with later settling to the bottom of the jar during observation over a period of three months. Yet the water that had been filtered through the polystyrene micro-bits into the second jar was still perfectly clear.

Illustrating use in filtering and improving a gaseous fluid, these polymer micro-bits also can be used as the packing in air filters by being admixed with suitable paper-making fibers and made up into sheets for loading into air filter frames.

Comparable liquid and gas filtering results are provided by micro-bits of a polyethylene.

Micro-bits of the other polyolefins are similarly useful.

Some batches of these polymer micro-bits of the invention produced, for example, by the above-described comminuting machine using a screen having circular openings of some sizes, are obtained with content of varying amounts from very little or at times up to 20% or so of fibrous particles still finer in size than that in the ranges described earlier above, for example, down to 15 microns or to 10 microns or so in width. Generally the presence of any such amounts of these smaller sizes may not introduce any disadvantage in the particular use that is to be made of the micro-bits.

However, if need be, these finer sizes can be removed by being filtered out by available screening or other suitable means, for example, a high capacity centrifugal sifter produced by the Kason Corporation, of Newark, New Jersey, U.S.A. This involves uniformly feeding the micro-bits by a feed screw discharging into a helical paddle rotating in a horizontally positioned cylindrical sifting chamber wherein centrifugal force accelerates movement of the micro-bit particles against the sieve which is attached to its supporting basket in a manner that allows the sleeve to vibrate freely.

In conducting the method of the invention, the operating conditions may cause an increase in temperature of the charge of expanded styrene-polymer or polyolefin bit-pieces being disintegrated in the comminuting zone. That may be more marked with some styrene-polymers than with others, so that in some of them the temperature rise may reach a level such that at it and higher the styrene-polymer bit-pieces would not readily or satisfactorily tear or shear under the particular operating conditions and possibly have a tendency to stretch or otherwise modify the reaction of the material being treatec and so adversely effect the desired tearing or shearing of the starting bit-pieces or what already has been torn or shorn from them. That is to be avoided, as by feeding more water with the bitpieces.

The finished comminuted polymer microbits leaving the comminutor manifest the property of holding onto water to the extent of from possibly 40 to 50 times their dry weight, and with its so held water forming a non-fluid plastic mass which is deformable and can roll, but without becoming fluid. The water is not released from this mass by draining or ordinary filtration, but requires pressure or suction, but yet it retains a significant amout of water. For example, some high pressure reduces the mass to a water content of only about 50 percent.

The proportion of water fed into the comminuting chamber then should be at least enough for the mixture of water and produced polymer micro-bits to be sufficiently fluid readily to flow through the orifices of the screen bottom of the comminutor. Conveniently the water should be from 55 to 100 times the weight of the produced expanded styrene-polymer micro-bits.

It is beneficial also to admix the starting expanded styrene-polymer or polyolefin bit-pieces with an amount of water sufficient substantially completely to wet their exposed surfaces before feeding them into the comminuting chamber.

It is advantageous also to the conduct of the method of the invention that the bit-pieces in the comminuting zone are driven by the impact surfaces alternately (i) to and against cornered edges of at least one pre-breaking or impact surface (of at least one pre-breaker bar described above), spaced circumferentially away from said orifices and radially similarly out of range of said impact surfaces as are said orifices, and then (ii) to and against said orifices.

It is also advantageous that the impact arms screens 13 and 17 covered by the felt sheets 24 and 31 respectively.

Intermediate the two pairs of respectively opposed idler rollers 28 and 32 and 29 and 31, this five-layered assembly passes between opposed pressure rollers 38 and 39, whereby their 56 cm. length applies a total pressure of, for example, 408 kilos (thus 7.3 kilos per centimeter, i.e. cm.) by pressure roller 38 against that assembly.

After felt sheets 24 and 31 separate at the junctions of rollers 29 and 33, the filter screens later separate as screen 17 passes down over idler roller 19. Then the micro-bits web reduced to a cake of 84 percent solids is removed from screen 17 by separator blade 40 and drops into micro-bits cake receiver 41. At the same time the first or upper filter screen 13 passes upwardly around idler roller 42 and any micro-bits cake adhering to that screen is removed from it by upper separator blade 43 and drops into micro-bits cake receiver 41.

Operating the foregoing water content reducing system with a 28 cm. in diameter and 56 cm. in length vacuum drum 11 at a speed of 10 revolutions per minute (r.p.m.) with a feed of 11.4 liters per minute of styrene-polymer micro-bits slurry (containing 2 percent of solids) from the comminutor provided a 3.175 mm.

thick wet micro-bits layer, and with the foregoing 7.3 kilos per cm. pressure by pressure roller 38 gave a yield of 10.9 kilos per hour containing 84 percent of solids as styrene-polymer micro-bits.

In its respective drying zone (not shown) each water absorbent sheet can be hot air (or suitably otherwise) dried and with preliminary passage between pressure rolls when its water content is high enough that a significant part of it can be expressed.

The foregoing system and apparatus for removal from micro-bits of water or other liquid inert to them is not limited to its just above described specific use on expanded polystyrene micro-bits. The method and system also are applicable similarly to micro-bits of any of the other expanded styrene-polymers as well as to those of any polyolefin micro-bits. So also, the system is not restricted to the earlier above indicated dimensions or layout shown in the illustrative drawing, but can be modified to provide such other production capacity as is practical and variation in layout of the respec tive parts to meet particular requirements of plant production capacity and plant space accommodations.

This system for withdrawing such large con tent of water from the micro-bits is not limited to using a rotating vacuum drum to provide the web of high water content micro-bits to be passed through pressure rolls 38, 39 (Figure 16). Slurry-receiving tank 10 and vacuum drum 11 and its shaft can be eliminated and rollers 18, 20 and 21 moved to about the left of the former location of tank 10 with filter screen 17 correspondingly extended.

Then the highly liquid slurry product from the comminutor is fed to a feed box (similar to the head-box from which paper pulp is fed to the fourdrinier in paper making), located above filter screen 17 (slightly to the right of roller 18) and discharging onto that screen. There the free water accompanying the micro-bits drains through the early portion of screen 17 after passing over roller 18. Before screen 17 reaches pressure rolls 38 and 39 it passes over a suction box (much like that at the fourdrinier discharge end) where part of the water held by the micro-bits is withdrawn.

Roller 15 is moved somewhat to the right so as to be located just to the right of the extension upward from roller 18. Screen 13 is shortened and maintained taut by running under a roller replacing drum 11 and positioned adjacent to wire screen 17 as it travels past the suction box. The layer of wet micro-bits started on screen 17 is sandwiched between screens 13 and 17 as they continue after roller 18 to and through the nip between pressure rolls 38 and 39.

Water-absorbent sheets 24 and 31 beneficially are of cotton felt but can be of any other suitable water-absorbent sheet material having a greater affinity for water than the apparent surface tension holding the water to the micro-bits.

The comminuting machine is not limited to the specific details of the illustrative applicable unit described above. For example, the number of comminuting arms can be varied even up to 32 in relation to the specific plant production needs and the configuration of the housing can be modified accordingly. Some variation in certain parts of the comminuting arms also are possible. Those of its features which provide the effective comminuting function should be retained while allowing some variation in other areas of these arms. Also, the pre-breaker bars are not limited, for example, to the specific length or number, for either can be varied with respect to the specific production plan and in some cases they might be omitted.

The nature of the comminuting operation and the appearance of the micro-bits (as in Figures 1 to 5) show that the individual microbits particles have no significant uniformity in outline.

That the starting styrene-polymers and poly olefins (from a polyethylene to a poly-methylpentene), the expanded bit-pieces of which are converted into the micro-bits of the invention, are thermoplastic shows that they also are ex trudable.

That the micro-bits herein, even though hold ing a considerable amount of water (e.g. as much as about 80 percent), are said to be dry to-the-touch means that the micro-bits when touched do not wet the fingers or the palm of the hand when held in it.

Claims

WHAT I CLAIM IS:

1. A thermoplastic polymer which has been expanded and is non-brittle in expanded form selected from a styrene-polymer (as hereinbefore defined) and a polyolefin (as hereinbefore defined) from polyethylene to poly-methylpentene, which polymer is in the form of micro-bits which are (a) from 40 to 325 microns long and from 20 to 325 microns wide, (b) from substantially completely to entirely completely free of intact cells of the expanded polymer bit-pieces from which they were produced, (c) substantially without any uniformity in outline of the individual micro-bit particles, and (d) in density from 85 percent of, to substantially the same as, the specific unexpanded polymer from which there was provided the aforesaid expanded polymer.

2. Micro-bits as claimed in Claim 1, wherein said thermoplastic polymer is a styrene-polymer.

3. Micro-bits as claimed in Claim 2, wherein said styrene-polymer is polystyrene.

4. Micro-bits as claimed in Claim 3, wherein said expanded polystyrene is expanded prime polystyrene.

5. Micro-bits as claimed in Claim 3, wherein said expanded polystyrene is expanded scrap polystyrene.

6. Micro-bits as claimed in Claim 1, wherein said thermoplastic polymer is a polyolefin.

7. Micro-bits as claimed in Claim 6, wherein said polyolefin is a polyethylene.

8. Micro-bits as claimed in Claim 7, wherein said polyethylene is low density polyethylene.

9. Micro-bits as claimed in Claim 7, wherein said polyethylene is a melt alloy with by weitht about ten percent of polystyrene.

10. Micro-bits as claimed in Claim 6, wherein said polyolefin is a polypropylene.

11. Micro-bits as claimed in Claim 6, wherein said polyolefin is a copolymer of polypropylene with from 20 to 30 percent of polyethylene by weight.

12. Micro-bits as claimed in Claim 6, wherein said polyolefin is a melt alloy of polypropylene with a copolymer of polyethylene with up to 30 percent of said copolymer being polyvinyl acetate, and said polypropylene exceeding at least 50 percent of said melt alloy, said percentages being by weight.

13. An aqueous slurry of the micro-bits as claimed in Claim 1, which slurry contains by weight from one to two percent of said microbits.

14. An aqueous slurry as claimed in Calim 13, wherein said thermoplastic polymer is a styrene-polymer.

15. An aqueous slurry as claimed in Claim 13, wherein said thermoplastic polymer is polystyrene.

16. Micro-bits as claimed in Claim 1, which are dry-to-the-touch and contain by weight from 16 to 100 percent of solids as micro-bits and the balance being substantially only water.

17. Micro-bits as claimed in Claim 16, wherein said thermoplastic polymer is a styrene-polymer.

18. Micro-bits as claimed in Claim 17, where in said thermoplastic styrene-polymer is polystyrene.

19. The method of preparing micro-bits as claimed in Claim 1 from bit-pieces of said expanded thermoplastic polymer, which method comprises feeding into a confined comminuting zone, having a feed inlet thereto, expanded bitpieces of said expanded polymer and water, repeatedly impelling the resulting mixture of the starting bit-pieces in the water through a circular path by repeated impact on them in the water by a plurality of impact surfaces spaced apart from one another and rotated around the axis of said circular path at from 4,700 to 8,000 revolutions per minute.,and at the same time by said impact surfaces driving said expanded bit-pieces to and against corner-shaped edges of a dispersed plurality of orifices which may be (i) substantially circular having a diameter of from 0.102 to 3.175 millimeters, or may be non-circular having a minor dimension of from 0.254 to 3.175 millimeters and a major dimension of from 3.81 to 12.7 millimeters, and (ii) being arranged in screening array in an arcuate plane spaced radially out of range of said impact surfaces to an extent that need be only sufficient to avoid collision between said orifices and said impact surfaces, and thereby repeatedly tearing, ripping and shearing microbits of the expanded polymer from said bitpieces thereof; said fed in water being so proportioned to said fed in expanded polymer bitpieces to prevent the content of the comminuting zone from reaching a temperature that would adversely effect the starting properties of said starting bit-pieces that enable providing said micro-bits.

20. The method as claimed in Claim 19, wherein said arcuate plane in which said orifices are arranged and said impact surfaces are spaced apart by from 0.518 to 1.016 millimeter

21. The method as claimed in Claim 19 or 20, wherein the surfaces of said expanded thermoplastic polymer bit-pieces are wetted with water prior to their being fed into said comminuting zone.

22. The method as claimed in Claim 19, wherein said impact surfaces are axially and also angularly spaced apart from one another.

23. The method as claimed in Claim 19, wherein said expanded thermoplastic polymer bit-pieces in said comminuting zone are driven by said impact surfaces alternately (i) to and against cornered edges of at least one pre-breaking surface located between said feed inlet and said plurality of orifices and spaced circumferentially away from said orifices and radially similarly out of range of said impact surfaces as are said orifices, and (ii) to and against said orifices.

24. The method as claimed in Claim 23, wherein there is a plurality of said pre-breaking surfaces and they are elongated and extend for about the width of said comminuting zone parallel to the exis of said circular path and are circumferentially spaced apart from one another about said axis.

25. The method as claimed in Claim 19, wherein the ratio of the water fed with said thermoplastic polymer bit-pieces into said comminuting zone is from 55 to 100 times the weight of the starting styrene-polymer bit-pieces.

26. The method as claimed in Claim 19, wherein said micro-bits leave said comminuting zone as a slurry of them in water, containing at least one percent of said micro-bits as solids, and said slurry is subjected to vacuum filtration thereby to increase the solids content to at least 16 percent by weight.

27. The method as claimed in Claim 19, wherein said micro-bits continuously leave the comminuting zone as a slurry in said water, which slurry then is applied to a surface of a moving continuous first sheet of a non-waterabsorbent foraminous member continuously to provide on said first surface a removably adhering continuous web of partially de-watered micro-bits, applying suction to the other surface of said first foraminous member to withdraw therethrough part of the water from said web of micro-bits, covering the initially uncovered surface of said web of micro-bits with one surface of a second moving continuous sheet of a non-water-absorbent foraminous memberto provide a moving sandwith of said micro-bits web between the opposed facing surfaces of both of said foraminous members, and the exposed surface of each of said foraminous members continually is covered by a continuous run of a water-absorbent sheet material having a stronger absorbent affinity for water than the surface tention holding the water to the microbits, and the resulting five-layered assembly sequentially is passed through the nip between opposed rollers of a pair of pressure rollers constituted to provide against the five-layered assembly sufficient pressure to enhance significantly the absorption attraction of the water by the water-absorbent sheet material from said web of micro-bits; and as the consecutive portions f the five-layered assembly leave said pressure rollers, removing the microbits from said foraminous sheet material, thereby providing a micro-bits product consisting by weight of from 50 to 90 percent microbits solids.

28. The method as claimed in Claim 27, wherein said slurry of micro-bits in water con tinuously is fed into a liquid confining zone wherein there is supported a rotatable vacuum drum partially immersed in a body of said slurry maintained in said zone, and said first non-water.

absorbent foraminous member passes into that body of slurry maintained in said confining zone and around under and in contact with the immersed part of said rotating vacuum drum whereby as suction is maintained in said drum as it rotates in said body of slurry with said first foraminous member moving in contact with the drum, a continuous layer of waterholding micro-bits continuously is provided along that foraminous member and as the latter leaves that body of slurry and approaches the second foraminous member, the layer of water-holding micro-bits is sandwiched between both of said foraminous members as both of them come close enough for the second fora minous member to meet tnd continue in con tact with that layer of water-holding micro-bits.

29. The method as claimed in Claim 27, wherein after the micro-bits are removed from between said foraminous members, the water absorbent sheet material is treated to remove water from it before returning again to contact the exposed surface of its respective one of said foraminous members between which is sandwiched a further amount of micro-bits from which water is to be absorbed.

30. The method as claimed in Claim 19, wherein said expanded thermoplastic polymer is selected from a styrene-polymer and a poly olefin from polyethylene to a poly-methylpen tene.

31. Micro-bits of an expanded, thermo plastic, non-brittle is expanded form polymer substantially as described and shown in the drawings.

32. The method of preparing micro-bits as claimed in Claim 19, substantially as described and shown in the drawings.