JPH0542546A - Purging material for molding machine and purging method - Google Patents

Abstract

PURPOSE:To clean a molding machine efficiently by purging the machine with a thermoplastic resin compound in which a fibrous filler of 2mm or more in length is mixed in an amount of 10-80wt.% of the compound. CONSTITUTION:A purging material of a resin compound in which a fibrous filler of 2mm or more in length is mixed with a thermoplastic resin in an amount of 10-80wt.% of the compound is added into a molding machine. The molding machine is purged by plasiticizing the purging material with rotating the screw. In this process, the fibrous filler in the purging material is entangled into a cotton shape to effect brushing, scraping off deposits on the screw and cylinder of the machine. The deposits scraped off are incorporated into the cotton-shaped filler to be discharged from the machine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a purging material and a purging method for a plastic molding machine. The molding machine referred to here also includes an extrusion molding machine (extruder) used for melt-kneading and the like of resins.

[0002]

2. Description of the Related Art In extrusion or molding of plastics, when switching resins, or when disassembling and cleaning the molding machine, etc., the resin and the resin adhering to the inside of the cylinder or the screw or addition It is necessary to completely remove heat-deteriorated adhered substances and the like, and usually a method of removing these adhered substances by flowing a purge material into the cylinder is adopted.
As the purge material, a material made of polymethylmethacrylate resin is widely used. Further, as another purge material, JP-A-54-29351 discloses a purge material composed of a partially gelled cross-linked polyethylene resin, and JP-A-58-125732 discloses a specific purge material. Purge material containing organic phosphorus compound, JP-A-2-60727
The publication discloses a purge material containing a polyamide-based resin having a specific terminal group as a main component. However, it is hard to say that the effects of these purge materials are still in a satisfactory stage, and in particular, in terms of the removal of the resin or the resin strongly adhered to the cylinder or the screw, the thermally deteriorated adhered matter such as the additive, and the like, You will get poor results.

On the other hand, as a method for removing the above-mentioned deposit adhered to the groove of the cylinder or screw of the molding machine,
Using a resin containing short glass fibers as the primary purging agent, the edge effect of the glass fibers is used to physically scrape off the deposits, and then the secondary washing with the target resin is often used to replace the resin. Has been done. However, also in this method, since the glass fibers in the primary purge material are short fibers and most of the glass fibers are buried in the resin even in the plasticized state, the efficiency of scraping off adhered substances is not so high. It is not good, and the adhered matter that has been scraped off is not compatible with the matrix resin of the purge material, so it will separate and easily adhere to the cylinder or screw again. Use a large amount of purge material to obtain a sufficient effect. There was a drawback that it was necessary.

As described above, with the conventional purging material and purging method, it is difficult to efficiently replace the resin of the molding machine or clean the cylinder and the screw, which results in productivity in extrusion or molding. It is also a factor that lowers the quality of the molded product and further impairs the quality of the molded product, and its improvement has been desired.

[0005]

Means for Solving the Problems The present inventors have solved the above-mentioned problems of the prior art and have improved productivity, improved quality and personnel by efficiently performing resin replacement of a molding machine or cleaning of cylinders and screws. As a result of earnest research for the purpose of cost reduction, it was found that this object can be achieved by using a resin containing a specific amount of a fibrous filler having a specific length or more as a purge material, and the present invention is achieved. Arrived That is, the present invention uses a purging agent for a molding machine and a purging agent comprising a resin composition in which 10 to 80% by weight (in the composition) of a fibrous filler having a length of 2 mm or more is mixed with a thermoplastic resin, The present invention relates to a purging method for a molding machine, which is characterized by plasticizing and purging.

The thermoplastic resin used in the purge material of the present invention is not particularly limited, and includes olefin polymers (polyethylene, polypropylene, etc.), polystyrene, AS resin, ABS resin, acrylate-based or methacrylate-based polymers (polymethyl). Methacrylate etc.), polyamide, polyester (polyethylene terephthalate, polybutylene terephthalate etc.), polyacetal, polycarbonate, polyurethane, polyphenylene sulfide, etc., and one or more kinds selected from known thermoplastic resins and modified products of these resins. Can also be used. Among these resins, from the viewpoint of efficiency as a purging material, as the matrix resin constituting the purging material, the same or the same series of thermoplastic resin as the resin to be newly extruded or molded after cleaning is used. However, some of these resins are expensive and lack versatility. Therefore, considering the cost of the purge material, the ease of replacement of the resin by the resin that is used for extrusion and molding after purging, and the cleaning efficiency in the molding machine, heat deterioration of the matrix resin that constitutes the purge material is considered. Olefin-based resins such as polyethylene and polypropylene, polystyrene, acrylic resins (AS etc.), (meth) acrylate-based resins (PM)
MA and the like) are preferred because of their high versatility.

Next, the fibrous filler to be mixed is not particularly limited, and any of glass fiber, carbon fiber, metal fiber, high melting point (high softening point) organic fiber and the like can be used, but the cost is low. Considering the cleaning efficiency of the molding machine and the like, glass fiber is particularly preferable. The fibrous filler may be treated with a sizing agent or a surface treatment agent.

The purging material of the present invention comprises a resin composition containing 10 to 80% by weight (in the composition) of a fibrous filler having a length of 2 mm or more selected from such fibrous fillers, The feature is that a long amount of long fiber is mixed. Short fibers may be blended in an appropriate amount as long as these conditions are satisfied. The purge material of the present invention is a kind of "scrubbing brush" (or "brush") having a high porosity when the resin is melted and the fibers are entangled in a cotton shape when it is supplied to a molding machine and plasticized while rotating the screw. ) Is formed, thereby improving the efficiency of scraping off the resin or adhered matter adhered to the cylinder and the screw. The formation of such a cotton-like material having a high porosity by the purging material of the present invention is completely different from the form of the plasticized product when the short fiber-containing resin is used as the purging material, and its effect is far from expected. It is as excellent as that.

The length and blending amount of the fibrous filler in the purging material of the present invention are mainly determined by the degree of entanglement of the fibers when the purging material is plasticized and the efficiency of scraping off the adhered resin or the adhered material due to this. It is decided based on the result of examination. That is, when a fibrous filler having a fiber length shorter than 2 mm is used, it is difficult to form a state having a high porosity due to the cotton-like entanglement of the fibers, and since the fibers are short, they are not mixed in the molten resin. It is buried and cannot obtain sufficient scraping efficiency. The preferred fiber length is 3 mm or more, more preferably 5 mm or more. Also, if the amount of the fibrous filler compounded is less than 10% by weight, the formation of a cotton-like material having a high porosity due to the entanglement of fibers becomes insufficient, and moreover, there are few fiber end portions exhibiting a scraping effect, which is sufficient. Scraping efficiency cannot be obtained.
On the other hand, if the content of the fibrous filler exceeds 80% by weight, not only is it difficult to prepare the composition, but also the load on the molding machine when purging using the composition is significantly increased, which is not preferable. Taking these balances into consideration, the preferable amount of the fibrous filler is 20 to 70% by weight, and particularly preferable.
30 to 65% by weight. Further, in the purging material of the present invention, in order to efficiently perform the cotton-like entanglement of the fibers, it is preferable that the blended fibrous filler has a uniform length.
Further, in view of the penetration of the purge material into the forming machine and the plasticization efficiency in the molding machine, the purge material is preferably in the form of pellets having a length of 2 to 50 mm. From this point of view, in the present invention, the purging material is a pellet having a length of 2 to 50 mm,
It is preferable that the fibrous filler has a structure in which the fibrous filler has substantially the same length as the pellet and is arranged substantially parallel to the length direction of the pellet, and particularly preferably, a length 3 having the same structure.
It is in the form of pellets of ~ 30 mm. The resin composition having such a specific structure can be easily obtained by a method such as pultrusion molding.

The purging material of the present invention is a known substance generally blended with a thermoplastic resin, for example, a stabilizer such as an antioxidant or an ultraviolet absorber, a plasticizer, and a crystallization accelerator within a range not impairing its purpose. It is also possible to appropriately add an agent or a fibrous, plate-like, powdery or granular filler according to the purpose, but an additive which may contaminate the molding machine due to its blending, for example, a colorant is not blended. Often it is better.

The method for producing the purge material of the present invention is not particularly limited, but the method by drawing as described above is particularly preferable because the production is easy and the fiber length of the obtained purge material is uniform. Is the way. In order to purge the molding machine with such a purging material and discharge and remove the resin or adhered matter adhering to the cylinder or screw, the purging material is supplied to the molding machine, plasticized while rotating the screw, and the outside of the molding machine. The extremely simple operation of discharging into the air is sufficient. At this time, the fibrous filler is entangled to form a cotton with a high porosity, and as a kind of "scrubbing brush (or brush)", it exerts an effect of scraping off the resin or adhered matter adhered to the cylinder or screw.

Further, in the purging material of the present invention, since the long fibrous filler is used, the cotton having a lot of spaces naturally becomes entangled in the plasticizing process, so that the scraped-off deposits become cotton-like. By being taken into the central portion (space portion), the chance of coming into contact with the metal surface again and adhering to the metal surface is reduced, and as a result, it is easily discharged to the outside of the molding machine. As a result, it is not necessary to specify the matrix resin of the purge material, and there is no particular restriction on the mating resin to be cleaned, which is very common. The purge material of the present invention is
Like a screw type injection molding machine or a single screw extruder,
When applied to a material that plasticizes the resin under an appropriate shearing force, the cotton-like material is efficiently formed by the entanglement of fibers, and the function as a purge material is more effectively exhibited. , Particularly preferred.

[0013]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 and Comparative Example 1 First, polypropylene black pellets were injection-molded by an injection molding machine.

Next, a pelletized polypropylene resin composition having a length of 12 mm, which is obtained by pultrusion and contains 40% by weight of glass fibers aligned in the length direction (the fiber length of the glass fibers is also substantially 12 mm). Is used as a purge material,
The injection molding machine was purged, and the weight of the injected resin was measured until the color of the injected resin was substantially eliminated.
On the other hand, for comparison, a polypropylene resin composition reinforced with 40% by weight of glass short fibers (dispersion fiber length: about 0.3 mm) was used as a purge material, and the same test was performed. The results are shown in Table 1.

[0016]

[Table 1]

The screws, cylinders, etc. of the injection molding machine after purging in Example 1 were much less dirty than those in Comparative Example 1 and had a clean gloss.

Example 2 and Comparative Example 2 A blow molding machine was used to blow mold a polyphenylene sulfide resin. Next, obtained by pultrusion molding, using a pelletized polypropylene resin composition having a length of 12 mm containing 40% by weight of glass fibers aligned in the length direction as a purging material, and after purging, a polypropylene for blow molding Blow molding was performed, and the number of shots until the black matter (black spec) mixed in the obtained molded article and scattered was not examined was examined. On the other hand, for comparison, the same test was performed using the purge material made of the same short fiber reinforced polypropylene resin composition as in Comparative Example 1. The results are shown in Table 2.

[0019]

[Table 2]

[0020]

As is apparent from the above description and the examples, if the purging material of the present invention comprising a thermoplastic resin and an appropriate amount of a fibrous filler having a specific length or more is blended, it is plasticized. While purging, the fibrous filler became entangled and became cotton-like, and as a kind of "scrubbing brush" or "brush", it exerted the effect of scraping off the deposits on the screw and cylinder and was scraped off. Since the adhered substances are taken into the cotton-like material and discharged to the outside of the molding machine, extremely efficient cleaning of the molding machine becomes possible. This has the advantage that the workability at the time of replacing or cleaning the resin of the molding machine is improved, not only improving the productivity but also improving the product quality.

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Claims (4)

[Claims] 1. A purging material for a molding machine, which comprises a resin composition containing a thermoplastic resin and 10 to 80% by weight (in the composition) of a fibrous filler having a length of 2 mm or more. 2. The purging material is in the form of pellets having a length of 2 to 50 mm, and the fibrous filler is substantially the same length as the pellets and arranged substantially parallel to the longitudinal direction of the pellets. Purging material for molding machines. 3. A purging material comprising a thermoplastic resin and a fibrous filler having a length of 2 mm or more in an amount of 10 to 80% by weight (in the composition) is used, and the purging material is supplied to a molding machine. Then, the method of purging a molding machine is characterized by plasticizing while rotating the screw and purging. 4. The resin composition is in the form of pellets having a length of 2 to 50 mm, and the fibrous filler is substantially the same length as the pellets and arranged substantially parallel to the length direction of the pellets. 3. The method for purging a molding machine according to item 3.