RU2697332C1 - Method of producing articles from composite material based on polyamide - Google Patents

Abstract

FIELD: manufacturing technology.SUBSTANCE: invention relates to production of articles from composite materials based on polyamide. Technical result is achieved by method of making articles from composite material based on polyamide, which includes heating of main initial component containing caprolactam, obtaining working mixture containing caprolactam, a polymerisation catalyst and an activator, filling the working mixture into a preheated casting mold. Main initial component is a suspension of single-wall carbon nanotubes in caprolactam, and the working mixture is obtained by successive mixing of the main initial component with a polymerisation catalyst and an activator.EFFECT: wider range of controlling viscosity of monomers when producing parts from polyamides.15 cl, 1 dwg, 1 tbl, 3 ex

Description

The invention relates to technologies for producing products from composite materials based on polyamide containing carbon nanotubes.

Since polyamides are characterized by high strength as well as resistance to environmental influences, the invention can be used in various industries for the production of high-strength products, including engineering, medicine, the automotive and aviation industries.

Polyamides are prepared in various ways, including polycondensation of diamines and dicarboxylic acids, polycondensation of higher amino acids, or diamines with dicarboxylic acids, condensation of caprolactam and salts of diamines of dicarboxylic acids.

The most common methods for producing parts from polyamide are injection molding and reactive injection molding (RIM technology). The main difference between RIM technology and the method of manufacturing products from thermoplastics by injection molding is that the initial semi-finished product loaded into specialized equipment is not polymer granulate, but a reaction mixture obtained by mixing in a predetermined ratio of several liquid low molecular weight components. This mixture is fed into the mold, where a chemical reaction of the interaction of the components occurs with the simultaneous formation of the finished polymer product. The main source component of the raw materials for the RIM technology of polyamides is the monomer caprolactam, to which an activator, catalyst and other additives are added. Thus, for the manufacture of polyamide products using RIM technology, additional time and energy are not required for the intermediate stages of the process - polymer synthesis, granulation of the polymer material and repeated thermal effects on it (drying, melting).

RIM technology runs at relatively low temperatures and pressures. Another important advantage of RIM technology is the ability to manufacture products from polyamide with complex shapes with wall thicknesses up to 40-50 mm and dimensions up to 1500 × 2000 mm and more. The cost of injection molds for products manufactured according to RIM technology is an order of magnitude lower than for similar products obtained by injection molding. Injection molds are more thin-walled, but require heating. The molding process takes 3-5 minutes.

This process relates to high-performance methods for producing polymer products, but has some disadvantages. The main problem of RIM technology is the low viscosity of caprolactam melt, which is 9 cP. Meanwhile, for the implementation of the process according to RIM technology, the monomer viscosity should be at least 50 cP, and the most preferred value is at least 1500 cP. To increase the viscosity, various additives are added to caprolactam, which increase the viscosity, but at the same time worsen the physical and mechanical properties of the polyamide product.

Known methods for the manufacture of products using RIM technology in which to increase the viscosity of the melt in the manufacture of composite materials offer to add resin, [US Application No. 201527277777, IPC: B29B 11/16, B29C 45/14, US Application No. 20150165651, IPC: B29C 35/02; B32B 27/12]. However, the addition of resin increases the viscosity of caprolactam, but impairs the physical and mechanical properties of polyamides. In addition, the addition of resins does not allow a wide regulation of the viscosity of the monomers for the RIM method of producing parts from polyamide.

There is also a method of producing a reinforced composite material by injection molding [US Application No. 201330001817 A1, IPC: B29C 45/14]. This process takes place at relatively high temperatures and pressures. This increases the demand for molds used for polymerization and often does not allow the use of standard equipment used for compression molding.

The prototype of the present invention adopted a method of producing products from caprolactam, in which a mixture of A containing caprolactam, an epoxy resin and an activator is mixed with a mixture of B containing caprolactam and a catalyst. Vessels A and B are heated to 80 degrees and mixed to form a mixture C, then the resulting mixture is poured into a preheated form. [US Patent No. 4,400,490, IPC: C08G 69/00; C08G 69/18]. To increase the viscosity of the melt, the present invention proposes to add up to 25% epoxy resin. The disadvantage of the prototype is the negative impact of epoxy on the mechanical properties of the resulting product. Another disadvantage is the limited range of possible monomer viscosities obtained.

The present invention solves the problem of creating a method of manufacturing products from a composite material based on polyamide with the possibility of regulation over a wide range of viscosity of monomers when producing parts from polyamides.

The problem is solved in that a method for manufacturing products from a composite material based on polyamide is proposed, which includes heating the main starting component containing caprolactam, obtaining a working mixture containing caprolactam, a polymerization catalyst and an activator. The working mixture is poured into a preheated injection mold. The main starting component is a suspension of single-walled carbon nanotubes in caprolactam, and the working mixture is obtained by sequentially mixing the main starting component with a polymerization catalyst and an activator.

The concentration of single-walled carbon nanotubes (SWCNTs) in caprolactam is 0.001% - 10 mass. %

The viscosity of the suspension is at least 50 cP.

The polymerization catalyst can be alkali metals, in particular sodium, alkali metal hydrides, their oxides or hydroxides, or their compounds with caprolactam.

The concentration of the catalyst in the working mixture is 0.1-10 mass. %

As activator use isocyanates, or diisocyanates.

The concentration of activator in the working mixture is 0.01-10 mass. %

After heating the suspension, it can be purged with dry nitrogen, mixed, and then sonicated. For the production and mixing of a suspension of SWCNTs, an ultrasonic dispersant, or microfluidic processor, or high-speed mixer is used.

In order to increase the strength of the product from a composite material based on polyamide, a filler in the form of a fabric or fibers can be placed in the injection mold. The filler may be fiberglass, carbon fiber, or basalt fiber in a concentration of not more than 60 mass. % The mold is preheated to 150-160 ° C.

As a result of the anionic polymerization of caprolactam, a component is obtained from polyamide-6 with carbon nanotubes, or from a polyamide-6 filled with fibers with carbon nanotubes. The flexural strength of a composite product is at least 80 MPa; the bending strength of a composite material filled with fibers is at least 160 MPa.

In FIG. Figure 1 shows a graph of the dependence of the viscosity of the mixture on the content of single-walled carbon nanotubes.

The present invention allows you to change the viscosity of the molten monomer in a wide range, sufficient to obtain high-quality products. This reduces the requirements for molds used for polymerization and allows the use of standard equipment. The additive not only allows you to change the viscosity of the monomer, but positively affects the mechanical properties of the resulting composite. The method is cheap, cost effective.

Features of the invention are described in more detail in the following examples, which illustrate but do not limit the invention.

Example 1

Production of parts from polyamide-6 by reactive injection molding of caprolactam with the addition of SWCNTs. To obtain a suspension of single-walled carbon nanotubes in capralactam, 0.126 g of SWCNTs are placed in a glass with 40 g of caprolactam and heated on a tile to a temperature of 100-120 ° C with continuous blowing with dry nitrogen and stirring using a magnetic stirrer. Stirring is continued for 1 hour to remove moisture from caprolactam. Then the mixture is treated with ultrasound (US) at a power of 240 W for 10 min with a dry nitrogen purge and stirring.

Group, Germany), затем 0,8 г активатора С20Р. Смесь капролактама с ОУНТ, катализатором и активатором, перемешивают в течение 1 мин, затем заливают при помощи шприца в стандартную форму, предварительно нагретую до 150-160°С.To the resulting suspension, 1.2 g of CJ catalyst (production

Group, Germany), then 0.8 g of C20P activator. A mixture of caprolactam with SWCNTs, a catalyst and an activator is stirred for 1 min, then poured with a syringe into a standard form, preheated to 150-160 ° C.

This leads to the beginning of the polymerization of caprolactam, which ends in 10-15 minutes.

Next, the finished product is removed from the mold and kept at room temperature for 24 hours, and then measure their tensile strength.

Strength measurements of the obtained samples are carried out on a Shimadzu AGS-5-20KNXD tensile testing machine with a 20 kN strain gauge, in accordance with GOST 32656-2014.

The results obtained show that the tensile strength of a polyamide product without additives obtained by the anionic polymerization of caprolactam is at least 80 MPa. The tensile strength increases by about 15% with the addition of 0.3% SWCNTs.

Example 2

A mixture of caprolactam with SWCNT prepared by a method similar to that described in Example 1, before polymerization, is placed under pressure in fluoroplastic tubes with an inner diameter of 6 mm and a length of 120 mm. Then, the mixture is heated in tubes to a temperature of 150 ° C and polymerization is carried out directly in them. The resulting samples, which are solid rods with a diameter of 6 mm, are removed from the fluoroplastic tubes after cooling. Then, bending strength is measured. Bending strength measurements are made in accordance with GOST 4648-71. For polyamide samples without SWCNTs, the bending strength is 150 MPa. With the addition of 0.3% CNTs, the bending strength is 164 MPa. The increase in strength was about 10%.

Example 3

A mixture of caprolactam with SWCNT, prepared by a method similar to that described in Example 1, is used to fill under pressure a form consisting of fluoroplastic tubes with an inner diameter of 6 mm. The tubes are pre-filled with carbon fiber in the form of threads having a length not less than the length of the fluoroplastic tubes. Then caprolactam is polymerized and, after cooling, samples are removed from the mold and bending strength is measured.

For polyamide samples filled with carbon fiber with a concentration of 30%, the bending strength is 450 MPa. For polyamide filled with carbon fiber at 30% and CNT at a concentration of 0.2%, the bending strength is 590 MPa, i.e. strength increase was more than 30%.

The test results of the strength of the samples in bending are shown in Table 1.

Claims (15)

1. A method of manufacturing products from a composite material based on polyamide, comprising heating the main starting component containing caprolactam, obtaining a working mixture containing caprolactam, a polymerization catalyst and an activator, pouring the working mixture into a preheated injection mold, characterized in that the main starting component is suspension of single-walled carbon nanotubes in caprolactam, and the working mixture is obtained by sequentially mixing the main starting component with a catalyst and polymerization activator. 2. The method according to p. 1, characterized in that the concentration of single-walled carbon nanotubes in their suspension in caprolactam is 0.001-10 wt.%. 3. The method according to p. 1, characterized in that the viscosity of the suspension of single-walled carbon nanotubes in caprolactam is at least 50 cP. 4. The method according to p. 1, characterized in that the viscosity of the suspension of single-walled carbon nanotubes in caprolactam is at least 5000 cP. 5. The method according to p. 1, characterized in that the viscosity of the suspension of single-walled carbon nanotubes in caprolactam is at least 30,000 cP. 6. The method according to p. 1, characterized in that the polymerization catalyst is alkali metals, or hydrides of alkali metals, or their oxides, or hydroxides, or their compounds with caprolactam. 7. The method according to p. 1, characterized in that in the working mixture the polymerization catalyst is contained in an amount of 0.1-10 wt.%. 8. The method according to p. 1, characterized in that the activator are substances from the series: isocyanates or diisocyanates. 9. The method according to p. 1, characterized in that the activator is contained in the working mixture and in an amount of 0.01-10 wt.%. 10. The method according to p. 1, characterized in that the mold is preheated to a temperature of 110-180 ° C. 11. The method according to p. 1, characterized in that in the process of heating the main source component, a suspension of single-walled carbon nanotubes in caprolactam is purged with dry nitrogen, mixed and sonicated. 12. The method according to p. 1, characterized in that for the preparation of a suspension of single-walled carbon nanotubes in caprolactam using an ultrasonic disperser, or microfluidic processor or high-speed mixer. 13. The method according to p. 1, characterized in that before filling the working mixture into the injection mold, a filler in the form of a fabric or fiber is previously placed in it. 14. The method according to p. 13, characterized in that the filler is fiberglass or carbon fiber, or basalt fiber. 15. The method according to p. 13, or 14, characterized in that the filler content in the composite product is not more than 60 wt.%.

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