JP4271622B2 - Conveyor belt made of polyoxymethylene resin - Google Patents

Description

  The present invention relates to a conveyor belt formed of an assembly of fibers made of a specific polyoxymethylene copolymer.

  Synthetic resin conveyor belts are used in various industries.

  Conventionally, such a synthetic resin conveyor belt is generally made of a monofilament multi-woven fabric structure of polyester or polyamide. However, since polyester is inferior in alkali hydrolysis resistance and abrasion resistance, and polyamide has large dimensional changes and physical property changes due to water absorption, a conveyor belt made of such a resin is restricted in terms of the conveyed items and use conditions. There was a case.

  On the other hand, polyoxymethylene resin has a high degree of crystallinity, excellent wear resistance, bending fatigue resistance, rigidity, alkali resistance, alcohol resistance, etc. High expectations are placed on these materials.

  However, in the conventional polyoxymethylene resin, due to its crystallization characteristics, there is a great limitation in application to molding processing other than injection molding, and the production of fibers made of such resin is extremely difficult, A conveyor belt formed as an aggregate of the fibers has not been put into practical use. Further, due to the high degree of crystallinity of the polymer, there is a problem that when used as a conveyor, fibrillation tends to occur due to abrasion with the conveyed product, and sufficient practical durability cannot be obtained.

That is, although polyoxymethylene resin is a resin having excellent properties, it has been considered difficult to apply to industrial filament manufacturing because of its high crystallinity and high crystallization speed. . For this reason, except for academic research, it has hardly been the subject of research. The few known techniques related to twisted yarns that are processed products of such polyoxymethylene filaments are only related to twisted yarns having a fineness of 1000 denier or more (see, for example, Patent Document 1).
JP-A-61-146832

  The object of the present invention is to solve the above-mentioned problems, and has a high degree of crystallinity, and is a transport conveyor made of polyoxymethylene resin that has excellent wear resistance, bending fatigue resistance, rigidity, alkali resistance, alcohol resistance, etc. To provide a belt.

  As a result of intensive studies to achieve the above object, the present inventors have solved these problems at once by using a polyoxymethylene copolymer having a specific composition with controlled crystallization characteristics, fluidity, etc. The present inventors have found that a conveyor belt having excellent wear resistance, hydrolysis resistance, durability, form stability, and the like can be obtained, and the present invention has been achieved.

  That is, the present invention includes a polymer chain mainly composed of repeating oxymethylene units containing 1.5 to 7 mol of oxyalkylene units represented by the following general formula (1) per 100 mol of oxymethylene units, and a melt index (190 ° C., It is a transport conveyor belt made of polyoxymethylene resin formed of an assembly of fibers made of a polyoxymethylene copolymer having a load of 2160 g) of 1.0 to 50 g / 10 min.

(Wherein, R _1, R ₂ is hydrogen, an alkyl group having 1 to 8 carbon atoms, an organic group having an alkyl group of 1 to 8 carbon atoms, a phenyl group, selected from an organic group having a phenyl group, R ₁ R ₂ may be the same or different, and m represents an integer of 2 to 6.)

  The conveyor belt obtained by the present invention is excellent in wear resistance, hydrolysis resistance, durability, shape stability, and the like, and is expected to be widely used in various industrial fields.

  Hereinafter, the present invention will be described in detail. As described above, the polyoxymethylene resin transport conveyor belt of the present invention is composed of 1.5 to 7 mol of the oxymethylene unit represented by the general formula (1) per 100 mol of oxymethylene units in a polymer chain mainly composed of repeating oxymethylene units. It is characterized by being formed of a fiber assembly made of a polyoxymethylene copolymer containing an alkylene unit and having a melt index (190 ° C., load 2160 g) of 1.0 to 50 g / 10 min.

  In such a polyoxymethylene copolymer used in the present invention, the ratio of the oxyalkylene unit represented by the general formula (1) is 1.5 to 7 mol per 100 mol of oxymethylene units, and preferably 1.7 to 100 mol per 100 mol of oxymethylene units. 6 mol, particularly preferably 1.8 to 5 mol per 100 mol of oxymethylene units. When the proportion of the oxyalkylene unit represented by the general formula (1) is reduced, the crystallization speed of the polyoxymethylene copolymer is increased, and many yarn breaks occur during spinning for the purpose of producing the fibers constituting the conveyor belt. Not only is this easy, but also the degree of crystallinity immediately after spinning is high, so that the stretchability is reduced, making it difficult to produce various filaments suitable for a conveyor belt. Moreover, the obtained fiber is likely to be cracked due to fibrillation when used as a conveyor belt, and becomes a conveyor belt having poor durability.

  On the other hand, if the proportion of the oxyalkylene unit represented by the general formula (1) is too large, the mechanical properties and the like of the polyoxymethylene copolymer are lowered, and the practical properties as a conveyor belt are insufficient.

  In addition, the polyoxymethylene copolymer used in the present invention has a melt index (MI) of 1 to 50 g / 10 minutes measured under a load of 2160 g at 190 ° C. according to ASTM D-1238, Is 1.2-30 g / 10 min, particularly preferably 1.5-20 g / 10 min. Note that there is a more preferable range of the melt index within the range of the melt index depending on the method for manufacturing the filament constituting the conveyor belt, and this point will be described later.

  A polyoxymethylene copolymer having an excessively high melt index (MI) is difficult to produce industrially stably, and has a low molecular weight and a melt viscosity that is too low. In the production of the above, melt processability is remarkably inferior in the process of decomposing and removing unstable ends by melt kneading, which is a conventional means, and in the stabilization process of blending a stabilizer and melt kneading with an extruder. Furthermore, since the molecular weight is low, the thermal stability and mechanical properties are inferior, the fiber constituting the conveyor belt is easily broken during spinning and drawing, and the production of the filament becomes unstable. On the other hand, a polyoxymethylene copolymer having an excessively low melt index (MI) has an excessively high melt viscosity, which increases the load during spinning and makes extrusion difficult.

  The production method of the polyoxymethylene copolymer as described above used in the present invention is not particularly limited. Generally, trioxane and a cyclic ether compound or a cyclic formal compound as a comonomer are mainly used as a cationic polymerization catalyst. It can be obtained by a bulk polymerization method. As the polymerization apparatus, any known apparatus such as a batch system or a continuous system can be used. Here, the introduction ratio of the oxyalkylene unit represented by the general formula (1) described above depends on the amount of comonomer to be copolymerized, and the melt index (MI) is a chain transfer agent used during polymerization, such as methylal. It can adjust with the addition amount of.

  Examples of cyclic ether compounds or cyclic formal compounds used as comonomers include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, epibromohydrin, styrene oxide, oxetane, 3,3-bis (chloromethyl) oxetane, tetrahydrofuran, Trioxepane, 1,3-dioxolane, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, etc. Ethylene oxide, 1,3-dioxolane, diethylene glycol formal and 1,4-butanediol formal are preferred. Further, the polyoxymethylene copolymer used in the present invention may have a branched or crosslinked structure.

  In the polyoxymethylene copolymer used in the present invention, the oxyalkylene unit represented by the general formula (1) formed by such a comonomer is dispersed as uniformly as possible in the molecular chain of the polyoxymethylene copolymer. It is preferable that the ratio of two or more oxyalkylene units represented by the general formula (1) chained is 5 mol% or less of the entire oxyalkylene units.

  The polyoxymethylene copolymer obtained by polymerization is subjected to catalyst deactivation treatment, removal of unreacted monomers, polymer washing, drying, stabilization of unstable terminal portions, etc., and various stabilizers. Stabilization treatment by blending is performed for practical use. Typical stabilizers include hindered phenol compounds, nitrogen-containing compounds, alkali or alkaline earth metal hydroxides, inorganic salts, carboxylates, and the like.

  Furthermore, the polyoxymethylene copolymer used in the present invention may be added to general additives for thermoplastic resins, for example, coloring agents such as dyes and pigments, lubricants, nucleating agents, release agents, charging agents, if necessary. One or two or more of an inhibitor, a surfactant, an organic polymer material, an inorganic or organic filament, plate, or granular filler is added within a range that does not impair the object of the present invention. Can do.

  Next, the manufacturing method of the fiber which comprises the conveyance conveyor belt made from polyoxymethylene resin of this invention is demonstrated.

  Monofilament or multifilament is used as the fiber constituting the conveyor belt, but the production method is not particularly limited, and general melt spinning and stretching production methods can be used. Here, in the case of a monofilament, it is preferable to use a melt index (MI) having a melt index of 1 to 30 g / 10 min, and more preferably 1.5 to 15 g / 10 min. In the case of multifilaments, those having a melt index of 1 to 30 g / 10 min are preferably used, and more preferably 3 to 20 g / 10 min.

  As an example of the filament manufacturing method, there is a method in which spinning is performed by winding a molten polymer discharged from a spinning device including a melt kneading device, a gear pump, a discharge nozzle, and the like with a roller. The filaments obtained in the spinning process can be subjected to a stretching process and can be stretched continuously or discontinuously.

The drawing ratio can be adjusted by appropriately setting the speed ratio between the unwinding roll and the winding roll, and a filament having a desired draw ratio can be obtained. The heating method at this time is not particularly limited as it is possible to use methods such as heated gas, heated liquid, hot plate contact, far infrared heating, laser light heating, electromagnetic induction heating, etc. As stretching conditions, it is preferable to stretch 2 to 40 times at a temperature not lower than the glass transition point and not higher than the melting point of the polyoxymethylene copolymer. The temperature during stretching is preferably about (melting point−50 ° C.) to (melting point−20 ° C.). If the heating is insufficient, the stretching stress increases and productivity is lowered, and yarn breakage is likely to occur. In an overheated state, the polymer is in a molten state and is undesirably broken, and the draw ratio is preferably set as appropriate according to the application within the above range. In setting the draw ratio, the strength of the stretched body obtained with an increase in the draw ratio is improved. For example, when considering a general balance of physical properties, for example, a draw ratio of about 5 to 10 times, or about 8 to 20 times when high strength is required, such as when used for woven warp It is preferable to draw at a high draw ratio.

  The filament obtained by the stretching process in the stretching process is preferably subjected to a heat setting process in which the molecular state is fixed in a heated state, whereby the dimensional change of the stretched body can be reduced. An example of the heat setting condition is heat setting at a temperature of (melting point−30 ° C.) or lower.

  In addition to the filaments (long fibers) described above, short fibers can also be used as the fiber aggregate constituting the conveyor belt. When short fibers are obtained, they can be obtained by crimping a stretched filament of 20 denier or less, if necessary, and cutting it to a length of about 10 mm to 100 mm.

  The transport conveyor belt made of polyoxymethylene resin of the present invention can be obtained by joining the both ends of a woven fabric obtained by weaving the above monofilament or multifilament with a loom, or by seamless weaving to obtain a cylindrical fabric. The function as a conveyor belt is expressed by rotating this continuously or intermittently with a general drive device for the purpose of conveyance. The weaving structure of the woven fabric is not particularly limited, and it is not limited to one layer of plain weave, twill weave, plain tatami weave, twill mat weave, multiple weave, and the like. Furthermore, a filament knitted fabric can also be used as a conveyor belt.

  In addition to using the woven fabric / knitted fabric as described above as a conveyor belt, the woven fabric and non-woven fabric are made by needling short and long fibers using a woven fabric / knitted fabric made of monofilament or multifilament as a base material. A composite tissue sheet of filaments and short fibers produced by compounding the tissue can also be used as a conveyor belt.

Moreover, when composing a woven fabric, other material filaments can be used for one part or all of warp and weft according to various purposes. As other material filaments, existing filaments such as polyester, polypropylene, polyamide, polyphenylene sulfide, and fluorine can be freely combined.
Moreover, after processing into a filament state or a conveyor state, it is also possible to implement various coatings, such as surfactant and a different polymer, according to the objective at the time of use.

  The conveyor belt of the present invention obtained as described above is excellent in abrasion resistance, hydrolysis resistance, durability, etc., and is a conveyor belt having a wide industrial application range.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.
Examples 1-7
Two with paddles using a continuous mixing reactor composed of a barrel that has a shape with two circular cross-sections and a rotating shaft with paddles. While rotating the rotating shafts of each at 150 rpm, liquid trioxane, cyclic ether or cyclic formal (1,3-dioxolane, 1,4-butanediol formal, diethylene glycol formal) is added as a comonomer, and methylal as a molecular weight regulator, At the same time, bulk polymerization was carried out while continuously supplying 50 ppm of boron trifluoride (based on the total monomers) to the polymerization machine to prepare polymers having comonomer amounts shown in Table 1. While rapidly passing the reaction product discharged from the polymerization machine through a crusher, the catalyst was deactivated by adding it to a 60 ° C. aqueous solution containing 0.05% by weight of triethylamine. Further, after separation, washing and drying, a crude polyoxymethylene copolymer was obtained.

  Next, 4 parts by weight of a 5% by weight aqueous solution of triethylamine and pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) are added to 100 parts by weight of the crude polyoxymethylene copolymer. ) Propionate] was added, and melt-kneaded at 210 ° C. with a twin-screw extruder to remove unstable parts.

  To 100 parts by weight of the polyoxymethylene resin obtained by the above method, 0.03 part by weight of pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] as a stabilizer and melamine 0.15 part by weight was added and melt-kneaded at 210 ° C. with a twin-screw extruder to obtain a pellet-shaped polyoxymethylene resin.

Using the polymer obtained, it was plasticized and melted by an extruder with a cylinder set temperature of 200 ° C. It was continuously extruded from a die with a diameter of 1 mmΦ, 6 holes, and a circular hole at a resin extrusion rate of 20 cc / min. In the process of drawing at a roll speed of 6 m / min, it was cooled and solidified by passing through a water bath at room temperature to obtain a rod-shaped molded body having a circular cross section, which was stretched in the length direction. Stretching is performed by adjusting the roll winding speed ratio in a hot air high-temperature furnace at 150 ° C under normal pressure. Specifically, the unwinding roller speed is controlled to 6m / min and the winding roller speed is controlled to 42m / min. As a result, the film was stretched 7 times. The filament obtained was made into a plain weave and subjected to wear resistance durability evaluation as a conveyor belt.
Comparative Examples 1-6
Using a polyoxymethylene copolymer outside the scope of the present invention, an unstretched body was prepared under the same conditions as in the example, and a monofilament prepared into a plain weave was evaluated in the same manner as the example.

  The results are shown in Table 1.

In addition, the evaluation items in the examples and comparative examples, the measurement methods, the evaluation criteria, and the like are as follows.
[Melt index (MI) measurement]
According to ASTM D-1238, measurement was performed at 190 ° C. under a load of 2160 g.
[Polymer composition analysis]
The polymer used for the physical property evaluation was dissolved in hexafluoroisopropanol d2, and ¹ H-NMR measurement was performed. It quantified from the peak area corresponding to each unit.
[Abrasion resistance durability evaluation]
As shown in Fig. 1, a SUS S55C 20mm diameter rod with a 200g weight fixed to the tip of a plain woven fabric with a width of about 10cm and a sandpaper # 2000 attached to the surface at a speed adjustable motor of 60rpm, After rotating for 10 minutes, the surface was visually observed.
* Criteria for observation results Judgment 5: No noticeable damage is observed on the filament surface.

  Determination 3 ... fibrillation is observed on the filament surface, and partial collapse is observed.

  Judgment 1 ... Significant damage is observed on the filament surface.

DO; 1,3-dioxolane BDF; 1,4-butanediol formal EGF; diethylene glycol formal

It is a figure explaining the test condition of abrasion resistance durability evaluation performed in the Example.

Claims (13)

The polymer chain mainly composed of repeating oxymethylene units contains 1.5 to 7 mol of oxyalkylene units represented by the following general formula (1) per 100 mol of oxymethylene units, and the melt index (190 ° C., load 2160 g) is 1.0. A transport conveyor belt made of polyoxymethylene resin formed of an assembly of fibers composed of a polyoxymethylene copolymer of ˜50 g / 10 min.

(Wherein, R _1, R ₂ is hydrogen, an alkyl group having 1 to 8 carbon atoms, an organic group having an alkyl group of 1 to 8 carbon atoms, a phenyl group, selected from an organic group having a phenyl group, R ₁ R ₂ may be the same or different, and m represents an integer of 2 to 6.) 2. The polyoxymethylene resin transport conveyor belt according to claim 1, wherein the polyoxymethylene copolymer contains 1.7 to 6 mol of the oxyalkylene units per 100 mol of oxymethylene units. 2. The polyoxymethylene resin transport conveyor belt according to claim 1, wherein the polyoxymethylene copolymer contains 1.8 to 5 mol of the oxyalkylene unit per 100 mol of oxymethylene unit. The polyoxymethylene resin transport conveyor belt according to any one of claims 1 to 3, wherein the polyoxymethylene copolymer has a melt index of 1.2 to 30 g / 10 min . The polyoxymethylene resin transport conveyor belt according to any one of claims 1 to 3, wherein the polyoxymethylene copolymer has a melt index of 1.5 to 20 g / 10 min . The polyoxymethylene copolymer transport conveyor belt according to any one of claims 1 to 5, wherein the polyoxymethylene copolymer has a branched or crosslinked structure . The aggregate of fibers is a non-woven fabric . The polyoxymethylene resin-made conveyor belt according to any one of claims 1 to 6 . The transport assembly belt made of polyoxymethylene resin according to any one of claims 1 to 6, wherein the assembly of fibers is a woven fabric formed from monofilaments . The transport assembly belt made of polyoxymethylene resin according to any one of claims 1 to 6, wherein the aggregate of fibers is a woven fabric formed from multifilaments . The transport conveyor belt made of polyoxymethylene resin according to any one of claims 1 to 6, wherein the aggregate of fibers is a composite of monofilament and nonwoven fabric . The transport conveyor belt made of polyoxymethylene resin according to any one of claims 1 to 6, wherein the aggregate of fibers is a composite of multifilament and nonwoven fabric . The polyoxymethylene resin transport conveyor belt according to any one of claims 1 to 6, wherein the fiber assembly is a monofilament or multifilament knitted fabric . A conveyor belt comprising the polyoxymethylene copolymer fiber assembly according to any one of claims 1 to 6 and other material fibers.

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