JPH0773958B2 - Eraser having thermoplastic material and method for producing the same - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an eraser having a thermoplastic material, which is a thermoplastic polyolefin copolymer, and a process for producing the same.

PRIOR ART West German Patent Application Publication No. 3043941 contains, in particular, a slightly crystallizable polyolefin graft copolymer elastomer prepared by the polymerization of ethylene and / or (α-) olefin. Such an eraser is described. This elastomer is mixed with factors, fillers and pigments and processed into an eraser. In addition, it is also possible in addition to the rubbers based on ethylene / propylene terpolymers, optionally also ethylene / propylene / diene terpolymers.

However, this type of eraser is remarkably aging-unstable due to the fact that in this case it is the essential ingredient Factis.
Furthermore, the eraser in this case does not contain a softening agent, so that the consistency of the base material cannot be adjusted arbitrarily. As a result, it is not possible to process these materials using any conventional eraser manufacturing equipment. Furthermore, in this case the hardness of the finished eraser can only be varied within relatively narrow limits.

DISCLOSURE OF THE INVENTION Therefore, the problem of the present invention is that the object of the present invention is not to have the above-mentioned drawbacks, and therefore is extremely resistant to aging, has good wear characteristics, and allows variable hardness adjustment within a wide range. And an eraser that can be manufactured with any conventional manufacturing equipment.

Means for Solving the Problems The above-mentioned problems can be solved by the eraser according to claim 1 and the method for producing the eraser according to claim 6. Advantageous embodiments of the eraser according to the invention are described in claims 2-5.

The synthetic components based on thermoplastic olefins containing embedded fully crosslinked rubber have proved to be very suitable for producing erasers. Erasers of this kind have all the desired characteristics and are simpler and cheaper to manufacture.

The synthetic components used in the invention and their preparation are known per se for several years, for example from US Pat. No. 4,130,535. However, since the mixture disclosed therein has been proposed for producing a hard vulcanized product having especially thermoplastic properties, it is immediately derived from the disclosure, always made with it, always flexible and It is entirely unthinkable that an eraser, which does not have to be thermoplastic in and of itself, has particularly good properties.

The thermoplastic olefin is polypropylene with in-situ polymerized ethylene-propylene-diene-monoolephine (abbreviation EPDM) and the rubber likewise consists of ethylene, propylene and unconjugated dienes, i.e. likewise of EPDM material. The case has proved to be particularly advantageous. The unconjugated diene is preferably ethylidene-
It may be norbornene, while the rubber should be crosslinked with sulfur, preferably having a degree of crosslinking of 7 × 10 ^-5 mol / ml and having a particle size of 0.5 to 2 μm, preferably 1 μm. Should be.

Further, as another additive or another binder, filler, softener or the like, styrene / butadiene block copolymer (SBS), styrene / isoprene rubber (SIS),
Ethylene / propylene copolymer and / or terpolymer (EP
M), polyvinyl chloride (PVC), ethylene ethyl acrylate and / or other plastics, and optionally, especially as a filler, chalk (calcium carbonate), zinc sulfide, magnesium oxide, barite, pumice powder, glass powder ,
Glass powders and / or factices and / or preferably also softeners, polybutadiene, polyalkylbenzenes, paraffinic or naphthenic oils-phthalates or other esters, and optionally inorganic or organic pigments as colorants Good.

The eraser according to the invention can be manufactured in a particularly simple manner as follows. First, in the first independent manufacturing process,
The synthetic component is prepared by first completely crosslinking the rubber, then embedding it in olefin and polymerizing with it. In this case, the polymerisation includes the polymerisation between the rubber and the olefin itself, and also the polymerisation of both. Thus, the finished synthetic component is a copolymer of polyolefin and fully polymerized and fully crosslinked rubber. This manufacturing process can be carried out externally, i.e. independently of the original eraser manufacturing. In some cases
This copolymer can be produced by a special manufacturer and provided as a commercial product.

The original eraser is then produced in a manner known per se. In this case, the previously produced copolymer is mixed as a synthetic component with another component having the entire composition until a homogeneous (dispersed) total mixture is formed.

The whole mixture is then plasticized and completely or partially molded in a customary manner using extruders, injection molding machines, plate presses or other production equipment and, if appropriate, subsequently cooled and brought to the desired size. Cut or shape.

EXAMPLES Next, the present invention will be described in detail with reference to Examples. in this case,
The quantity description is weight percent.

Example 1 (Example of composition range) Synthetic components (copolymer composed of polyolein and polymerized and completely crosslinked rubber) 5 to 50% Filler (calcium carbonate or other) 30 to 85% Factis 0 to 30% Other additives , Especially other thermoplastic plastics, eg SBS, SIS, PVC etc. 0-30% other additives, eg softeners, stabilizers, dyes or others 0-30% each particularly suitable individual amount being as specified in particular. The desired elasticity, mechanical strength, rigidity, hardness, wear resistance, texture and other final products are determined by the requirements for the eraser.

Example 2 (Production Example 1) 20% of the synthetic components, 40% of chalk and 40% of glass powder are mixed in a Henschelmischer for about 2 minutes.
This mixture is then plasticized in a counter-rotating double screw extruder at a temperature between 180 and 230 ° C. and formed into optionally shaped strands, which are cooled, for example in a water bath and subsequently as an eraser. Cut into regular size.

Example 3 (Production Example 2) 16% synthetic component, 8% styrene / butadiene block copolymer (SBS), 13% polyalkylbenzene and 63% chalk.
Is mixed with a high-speed stirrer in a Heinzmischer to generate frictional heat. At about 110 ° C, melting of the material occurs. The material is chilled and granulated at a temperature of 35 ° C. for milling and granulation. The granules are brought to the desired eraser shape in an injection molding machine and optionally cooled after demolding.

Example 4 (Production Example 3) Synthesis component 6%, SBS 8%, polyalkylbenzene 13.5%,
Chalk 63.5% and Factis 9% with a Heinz mixer
Heat to 130 ° C. and melt. After cooling, the pellets are plasticized and extruded in strands in an extruder at temperatures of 100 to 160 ° C., cooled and cut and optionally barreled.

Other mixed examples are summarized in the table below.

The synthetic compositions used and proposed in the present invention simultaneously form thermoplastics and act as binders, fillers or other mixing components in the eraser mixture.

Claims (6)

[Claims] 1. A completely crosslinked particle size of 0.5 to 2 .mu.m comprising (a) ethylene, propylene and a small amount of a non-conjugated diene.
5 to 50% by weight of polypropylene embedded with rubber having m, (b) 30 to 85% by weight of a filler consisting of chalk, zinc sulfide, magnesium oxide, barite, bismuth powder, glass powder and / or factice series (C) Softener, stabilizer and / or colorant 30% by weight or less,
And (d) styrene-butadiene block copolymer, styrene-isoprene rubber, ethylene-propylene copolymer and / or terpolymer, polyvinyl chloride, ethylene vinyl acetate, ethylene-ethyl acrylate or atactic polypropylene 30% by weight % Or less, an eraser having a thermoplastic substance. 2. An eraser having a thermoplastic material according to claim 1, wherein the non-conjugated diene constituting the component (a) is ethylidene-norbornene. 3. The rubber in component (a) is a sulfur cross-linking system of 7 × 10.
An eraser with a thermoplastic according to claim 1 which is crosslinked to a degree of crosslinking greater than ^-5 mol / ml. 4. Polybutadiene as the softening agent component (e),
Claim 1 containing a polyalkylbenzene, paraffinic or naphthenic oil and / or phthalate.
An eraser having the thermoplastic substance according to any one of items 1 to 3. 5. An eraser having a thermoplastic substance according to any one of claims 1 to 4, which contains an inorganic or organic pigment as a coloring component (c). 6. A completely crosslinked particle size of 0.5 to 2 .mu.m comprising (a) ethylene, propylene and a small amount of a non-conjugated diene.
5 to 50% by weight of polypropylene embedded with rubber having m, (b) 30 to 85% by weight of a filler consisting of chalk, zinc sulfide, magnesium oxide, barite, bismuth powder, glass powder and / or factice series (C) Softener, stabilizer and / or colorant 30% by weight or less,
And (d) styrene-butadiene block copolymer, styrene-isoprene rubber, ethylene-propylene copolymer and / or terpolymer, polyvinyl chloride, ethylene vinyl acetate, ethylene-ethyl acrylate or atactic polypropylene 30% by weight % Of a thermoplastic material having a thermoplastic content of at least 1%, wherein the component (a) is prepared by in situ polymerizing an ethylene-propylene-diene rubber embedded in polypropylene with the polypropylene, The components and the other components (b) and optionally (c) to (d) are mixed until a homogeneous total mixture is obtained, then plasticization and molding are carried out in the usual way by cooling, cutting or Performed on an extruder, injection molding machine, corrugated press or other suitable device, followed by a punching device. A method for producing an eraser having a thermoplastic material, which comprises: