RU2618255C1 - Method for producing glass-filled polyamide composition and glass-filled polyamide composition - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of obtaining glass-filled polyamide composition by extrusive combination of polyamide, stabiliser, chopped glass fiber and process lubricant at a temperature higher than polyamide melting point is described, followed by cooling and granulating the obtained composition, in which chopped glass fiber is introduced into polyamide melt in a zone, providing the length of extrusive combination of composition components from 2 to 16 diameters of extruder screw with the following component ratio wt. %: fiberglass 20.0-55.0; process lubricant 0.05-1.00; stabiliser 0.02-1.00; aliphatic polyamide - the rest is up to 100%. A glass-filled polyamide composition is also described.

EFFECT: glass-filled polyamide composition with increased fatigue endurance and strength level was obtained.

4 cl, 2 tbl, 10 ex

Description

The invention relates to manufacturing processes and prescription compositions of polymer composite materials based on aliphatic polyamides, which can be used for the manufacture of structural, electrical and general-purpose parts for automotive, aviation, special, engineering, electrical, household and other types of equipment.

A known method of producing glass-filled polyamides, in which glass fiber is introduced into the angular head of the melter of an extrusion machine, in which it is impregnated with a polyamide melt, followed by cooling and chopping of the formed glass-filled material into granules (USSR Author's Certificate No. 181296, class C08L 77/00 / class 39 s, 30; C08h /, declared on 11/18/1963, published on 04/15/1966). Produced according to the above, often called “cable” technology from stabilized polyamide grades PA6-211-14, PA6-211-15 or PA6-211-17 with a relative viscosity of 2.60-2.75 and a fiberglass content of 30-34 wt. %, glass-filled polyamide grade PA6-211-DS is characterized by a high level of strength properties (GOST 17648-83. Glass-filled polyamides. Technical conditions).

The main disadvantage of this method of producing glass-filled polyamides is the extremely low productivity (~ 300 kg per shift per process unit), which significantly increases the cost of the glass-filled material produced.

Despite the high strength properties, glass-filled polyamide grade PA6-211-DS has a number of disadvantages, mainly due to the "cable" method of obtaining it:

- poor technological properties that require the use of elevated temperatures and intensive screw plasticization during injection molding to homogenize the melt, which, in turn, imposes significant restrictions on the equipment used for its processing: the volume of the material cylinder of the injection machine must exceed the casting volume by 4- 6 times;

- the strength characteristics of products from PA6-211-DS significantly (up to 25%) depend on the technological parameters of injection molding, which reduces the strength of the products, especially when processing on obsolete equipment;

- in the process of warehouse storage, a decrease in strength characteristics for the first 1-3 years of storage reaches 30-35%, which requires an increase in the safety factor of products and, accordingly, an increase in the consumption of material and mass of products.

A known method of producing a reinforced polyamide composition by introducing into the worm plasticizer of the extruder an aliphatic polyamide, polypropylene or a mixture thereof with polyethylene and (or) ethylene propylene copolymer, a mixture of a copper salt and an alkali metal halide or 1,2,3-benzotriazole and a fatty acid amide, followed by introduction into the melt of the mixture of the indicated glass-roving components, co-extrusion of the components at a temperature exceeding the melting point of the polyamide, cooling and granulating the mixture (RF Patent No. 2152411, class C08L 7 7/00, C08J 5/08, claimed 02.16.1999, published 10.07.2000).

The disadvantage of this method of obtaining a reinforced polyamide composition is the low level of strength properties of the obtained compositions (yield strength in tension is 95-129 MPa, tensile stress in compression is 96-116 MPa), which does not allow them to be used for the manufacture of structural products.

The closest in technical essence and the achieved technical effect is a method for producing a glass-filled polyamide composition by co-extrusion of a mixture containing polyamide, stabilizer, fiberglass in the form of twisted or untwisted glass fibers, glass rovings or chopped glass fibers and calcium, barium or zinc stearate at a temperature exceeding the melting point of the polyamide, followed by cooling and granulation of the resulting composition having the following composition (RF patent No. 2076124, CL C08L 77/02, C08K 1 3/04, declared 04.24.1995, published on 03.27.1997):

polyamide 58.50-63.88 stabilizer 0.02-1.00 fiberglass 36.0-40.0 calcium, barium or zinc stearate 0.1-0.5

Many years of experience in the practical application of glass-filled polyamide grade Armamide PA 30-3M manufactured in accordance with this technical solution, showed that it is characterized by good manufacturability, has a high level of strength characteristics, is resistant to climatic factors and is widely used in the manufacture of products for various purposes in automobile-, machine-building, special and other types of equipment (Samoryadov A.V. Glass-filled polyamide of the Armamide grade PA 30-3M: processing, properties and // hostname Plastics -. 2001. - №6 -. pp 16-20).

The main disadvantage of this method is that the resulting glass-filled compositions have low resistance to shock-cyclic loads, i.e. low fatigue endurance. According to this indicator, Armamide PA SV 30-3M is significantly inferior to glass-filled polyamides obtained by the "cable" glass filling technology, in particular PA6-211-DS.

In addition, according to the level of static strength characteristics, Armamide PA SV 30-3M does not meet modern requirements for polymer materials for promising products of special equipment.

The disadvantages of this method and the resulting glass-filled materials should also include the fact that the best range of their strength properties is achieved in a fairly narrow range of glass fiber content (36-40 wt.%), Which limits the scope of these glass-filled polyamides.

An object of the invention is a significant increase in fatigue endurance and the level of strength properties of glass-filled polyamide compositions obtained by extrusion technology of combining components.

The technical solution of this problem is achieved due to the fact that in the method for producing a glass-filled polyamide composition by extruding a polyamide, stabilizer, chopped glass fiber and technological lubricant at a temperature higher than the melting temperature of the polyamide, followed by cooling and granulation of the resulting composition, the chopped glass fiber is introduced into the polyamide melt in the zone providing the length of the extrusion alignment of the components of the composition from 2 to 16 diameters of the screw of the extruder, with a trace following ratio, wt. %:

fiberglass 20.0-55.0 process grease 0.05-1.00 stabilizer 0.02-1.00 polyamide the rest is up to 100%

The technical result of the invention is also achieved due to the fact that the glass-filled polyamide composition for the manufacture of structural, electrical and general purpose products contains polyamide, stabilizer, chopped glass fiber and technological lubricant in the following ratio of components, wt. %:

fiberglass 20.0-55.0 process grease 0.05-1.00 stabilizer 0.02-1.00 polyamide the rest is up to 100%

The glass-filled polyamide composition may additionally contain ingredients selected from the group comprising organic, individual, oligomeric, polymeric substances and dispersed inorganic fillers, in an amount up to 7% by weight of the glass-filled polyamide composition.

The proposed production method and the composition of the obtained glass-filled polyamide materials are closely interconnected and provide a technical result - a significant (2-18 times) increase in fatigue resistance and a higher level of static strength characteristics of the obtained compositions in a wide range of formulations according to the composition.

To implement the proposed technical solution, the following components and substances can be used.

Aliphatic polyamides are used as the polymer matrix, preferably polyamide 6 with a relative viscosity of 2.4-3.6 and a content of low molecular weight and volatile substances of not more than 1.5 wt. %

As stabilizers for the resulting compositions, you can use thermal and light stabilizers of various structures based on:

- salts of monovalent copper (copper acetate, chloride, bromide and copper iodide), preferably in a mixture with an alkali metal halide, such as potassium iodide and others;

sterically hindered phenols or mixtures thereof, for example 1,6-hexanediol bis (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2,2'-methylene bis (4-methyl-6 tert-butylphenol), 2,6-di-tert-butyl-4-hydroxymethylphenol, 4,4'-methylene-bis- (2,6-di-tert-butylphenol), N, N'-hexamethylene-bis- 3,5-di-tert-butyl-4-hydroxyhydrocinnamide, 3,5-di-tert-butyl-4-hydroxybenzyl-dimethylamine and others;

- copper complex compounds, preferably in a mixture with alkali metal halides, for example, a mixture of a copper complex of triisoindolebenzenethtetramine with potassium iodide ("stabil-10") or a mixture of a copper complex of polyethyleneimine with magnesium chloride or potassium iodide ("MCS-21 thermal stabilizer"), etc. ;

- amine type compounds, for example N-isopropyl-N'-phenyl-n-phenylenediamine ("diaphen FP") or 2,2'-bis- (n-phenylaminophenoxy) diethyl ether ("thermostabilizer H-1");

and other thermal and light stabilizers suitable for use in polyamide compositions. It is also possible to use polyamides containing light and / or thermal stabilizers, for example, polyamides of the grades PA6-211-14 (N-1), PA6-211-15 (stabilization-10), PA6-211-17, PA6-311 -17 (ISS-21) and others.

As technological lubricants, it is possible to use the lubricants used for polyamide compositions (Kalinchev EL, Sakovtseva MB Effective injection molding of polymeric materials with lubricants // Polymer materials. - 2014. - No. 7. - P. 12-26 ): full and partial esters of monobasic fatty acids (C _12-28 ) and polyhydric alcohols, for example pentaerythritol tetrastearate, ethylene glycol distearate, ethylene glycol monostearate, glycerol monostearate, stearyl stearate; monobasic fatty acid amides, for example N, N'-ethylene-bis-stearamide; metal salts of fatty acids (metal soaps), for example, stearates of calcium, zinc, barium; organosilicon compounds - siloxanes, etc.

As the main filler, chopped glass fiber with a diameter of 5 to 15 μm, developed on direct sizing agents (i.e., containing effective sizing agents), suitable for producing glass-filled polyamide-based compositions, is used. It is preferable to use chopped glass fiber produced in granular and / or dosage forms, including granular glass fillers containing oligomers or polymers as a binder, for example, HST (granular glass filler of thermoplastics) based on low molecular weight polycarbonate or NTG (granular-based thermoplastics filler).

Almost all grades of dyes and pigments suitable for coloring aliphatic polyamides and produced in any final form can be used to color the resulting compositions: powders, pastes, concentrates of dyes or pigments on an oligomeric or polymer basis. A preferred outlet form is dye or pigment concentrates based on polyamide or polyethylene substrates. From the point of view of obtaining the highest level of properties, it is preferable to use organic dyes that do not impair the strength properties of glass-filled polyamides.

The polyamide composition may additionally contain organic individual, oligomeric or polymeric substances, introduced in an amount up to 7% by weight of the glass-filled composition, both independently and in the final forms of coloring components or chopped fiberglass. It is preferable to use individual organic substances, oligomers or polymers that belong to the group of physical (for example, organosilicon compounds, polyethylene, polysulfone, butyl rubber, etc.) or chemical (for example, PAIS-104 oligoamino maleimide or olefin copolymers having reactive groups ) polyamide modifiers. As additives, dispersed ones can also be used, including nanoscale, inorganic fillers in any final forms in quantities that do not lead to a decrease in the properties of the resulting compositions.

The proposed parameters of the production method and the ratio of the components in the resulting glass-filled polyamide compositions are optimal and ensure the achievement of a technical effect.

In the proposed method for producing polyamide compositions, the mixing zone of fiberglass with components is expressed in its length from the place of introduction of chopped fiberglass to the exit point of the melt of the composition from the extruder mixer, tied to the diameter of its screws, which allows reproducing the proposed technical solution on extruders of different capacities and sizes. The minimum mixing zone (2 screw diameters) is sufficient for compounding chopped fiberglass with other components, and exceeding the mixing zone over 16 screw diameters results in compositions with lower properties.

In order to achieve a better set of properties of the obtained polyamide compositions, it is preferable to introduce chopped glass fiber into the melt of a mixture of polyamide, stabilizer and technological lubricant. It is also possible to separately introduce the remaining components into the melt of the stabilized polyamide, for example, the introduction of a lubricant and / or various additional substances and fillers separately or together with chopped glass fiber.

When the content of fiberglass is less than 20 wt. % of the resulting compositions have an insufficient level of strength properties for use in the manufacture of parts for structural purposes, and over 55 wt. % - the effect of improving properties is less pronounced.

The stabilizer content in an amount of 0.02 wt. % is the minimum, providing thermal stability of the composition during processing, and the use of a stabilizer in excess of 1.0 wt. % does not enhance the stabilization effect, but leads to a rise in the cost of the resulting compositions.

When the content in the composition of technological lubricants exceeds the declared amount, the achieved effect of its action is not enhanced, and with a lower content than stated, the effect is not achieved.

The invention is illustrated by the following examples.

Example 1

7.96 kg of granulated polyamide grade PA6-210 / 310, pre-dried at 80-100 ° C to a moisture content of not more than 0.2%, is mixed with 35 g of thermostat H-1 and 5.0 g of calcium stearate. The resulting mixture was loaded into a Collin twin-screw laboratory extruder having 4 loading zones and a screw diameter of 40 mm, and was extruded at 240-270 ° C and a screw rotation speed of 50-80 rpm. Directly into the melt of the components through the loading zone, which ensures the mixing length of the components is 80 mm (2 screw diameters), 2.0 kg of chopped fiberglass based on glass fiber of the BS 10-84-78 structure are dosed and a rod of glass-filled material is obtained at the exit from the extruder forming head, which It is cooled and granulated. The composition and properties of the resulting composition are shown in table 1.

Studies of the strength properties of the compositions were carried out on standard samples, which were manufactured by injection molding on a Demg Ergotech Viva 50-270 injection molding machine in the following modes: casting temperature 240-280 ° C; casting pressure 90-100 MPa; mold temperature 80-90 ° C; holding time under pressure of 15-20 s; cooling time 20-25 s. Samples for testing after manufacturing were placed in two plastic bags, each of which was sealed, and kept until testing at room conditions from 16 to 48 hours. The time from the moment of extraction of the samples from the package to the end of the tests did not exceed 30 minutes.

The tensile strength was determined on type 2 blades according to GOST 11262-80. Bending stress at maximum load was determined on samples of size 4 × 10 × 80 mm according to GOST 4648-71, impact strength - according to GOST 4647-80 on samples of size 4 × 10 × 80 mm. The test results are processed statistically in accordance with GOST 14359-69. For the determination of each indicator of strength properties, 10-15 pieces of samples were tested.

Fatigue endurance, expressed in the number of loading cycles before the destruction of the sample, was determined by 2 methods. According to the first method, the fatigue endurance during shock cyclic bending was determined on a second-impact collar KPU-2 according to the following method: during testing, a 10 × 10 × 55 mm sample was placed on two supports and was subjected to transverse bending by a concentrated shock load with a frequency of 11.2 s ^-1 and the asymmetry coefficient R = 0. According to the second method, fatigue under the influence of a cyclic bending load (3-point bending) was determined on a universal testing machine of the Inspekt 50kN model, manufactured by Hegewald & Peshke, on standard samples of 4 × 10 × 80 mm in size. In each loading cycle, a fixed strain value of 6 mm was set, and the loading cycle was repeated after the sample was completely unloaded.

Example 2

The composition is obtained according to the procedure of example 1, but using polyamide grade PA6-211-15, containing stabilizer-10, chopped fiberglass grade EU 10-4.5mm-995, and the length of the mixing zone of the components is 160 mm (4 screw diameters) . The composition and properties of the resulting composition are shown in table 1.

Example 3

The composition is obtained according to the method of example 2, but chopped fiberglass brand DS 1103-10N and zinc stearate are used. The composition and properties of the resulting composition are shown in table 1.

Example 4

The composition is obtained according to the method of example 1, but using polyamide grade PA6-210 / 311, thermal stabilizer FP, chopped fiberglass grade EU 10-9mm-A93, and the length of the mixing zone of the components is 640 mm (16 screw diameters). The composition and properties of the resulting composition are shown in table 1.

Example 5

The composition is obtained according to the method of example 1, but chopped fiberglass CS7928 is used, and the length of the mixing zone of the components is 200 mm (5 screw diameters). In the initial mixture, a dye concentrate “brown caprozol 4K” made on low-pressure polyethylene (HDPE) is additionally introduced. The composition and properties of the resulting composition are shown in table 1.

Example 6

The composition is prepared according to the procedure of Example 5, but chopped glass fiber based on glass fiber of the BS 10-84-78 structure is used, pentaerythritol tetrastearate is used as a lubricant as an additional ingredient - PAIS-104 brand oligoamino maleimide concentrate on high pressure polyethylene (LDPE). The composition and properties of the resulting composition are shown in table 1.

Example 7

The composition is prepared according to the procedure of Example 5, but chopped glass fiber of the 451W grade is used, and calcite is used as an additional ingredient, which is introduced into the melt of the components together with chopped glass fiber. The composition and properties of the resulting composition are shown in table 1.

Example 8

The composition is prepared according to the procedure of Example 5, but a metered NTG chopped glass fiber containing a polysulfone-based binder is used. The composition and properties of the resulting composition are shown in table 1.

Examples 9-10 (for comparison).

The compositions are obtained by extruding the mixture of components, including polyamide 6 grade PA6-211-17, containing the MCS-21 thermal stabilizer, chopped glass fiber based on glass fiber structure BS 10-84-78 and zinc stearate, according to the methodology described in the prototype (RF patent No. 2076124). The composition and properties of the obtained compositions are shown in table 1.

As can be seen from the data of table 1, the proposed technical solution allows to obtain glass-filled polyamide compositions having, in comparison with the prototype, a higher resistance to shock-cyclic loads 2-18 times higher and 10-20% higher static strength characteristics in a wide range of formulations in composition.

The data in table 2 indicate that the glass-filled polyamide compositions obtained by the proposed technical solution surpass in their operational characteristics not only the “short-fiber” ones obtained by extrusion, but also the “long-fiber” glass-filled polyamides made by the “cable” technology, in particular, PA6- 211-DS, which is an unexpected result, since it is known that fiberglass fatigue is most significantly affected by the length of fiberglass (Manin V.N., Gromov A.N., Grigo evev VP Defectiveness and operational properties of polymeric materials. - L .: Chemistry, 1986. - 182 p.), which in the initial granules of glass-filled polyamide grade PA6-211-DS exceeds this figure by an order of magnitude for extrusion polyamides, for example Armamide PA SV 30-3M.

An even greater advantage of the proposed compositions compared to the prototype and analogue is observed as a result of storage of samples of materials in an unheated warehouse in the climatic zone of the Moscow Region (table 2). To obtain a real picture of the behavior of the compositions directly under operating conditions, the samples were not subjected to conditioning to the initial moisture level before testing. As can be seen from the data in table 2, in the initial state, the claimed composition in fatigue endurance exceeds glass-filled polyamide grade PA6-211-DS 1.7 times, and after 1 year of storage this superiority increased to 4.6 times, which indicates high climatic stability the resulting compositions and, accordingly, high operational stability of products from this material.

Despite the popularity of the individual components of the method for producing glass-filled polyamide compositions described in the above sources, namely the use of chopped glass fiber and the procedure for introducing glass fiber in the form of roving directly into the polyamide melt, in the proposed method, a combination of technological and technical solutions was found that ensured a significantly higher , a priori not expected, technical effect leading to the production of glass-filled polyamides with high-quality about new features that surpass the best counterparts. In this regard, it is important to note that such a result was achieved using available raw materials and extrusion equipment available at Russian enterprises, which makes it possible to implement development in industrial production without large financial costs.

The practical application of glass-filled polyamide compositions obtained in accordance with the proposed technical solution will significantly expand the field of practical application of glass-filled polyamides, increase the operational reliability and warranty periods of a wide range of products for both special and general technical purposes.

The examples provided in the present description only demonstrate the feasibility of the proposed technical solution, but do not limit the scope of claims described in the claims. The claims cover the main features of the present technical solution, and various options and modifications of the production process and its process parameters, for example, changing the sequence of introducing a stabilizer polyamide into the melt, technological lubricant and / or additional ingredients, changing the temperature parameters of extrusion, as well as the use of those not mentioned in the present description of the ingredients, the specification of their quantitative content (up to 7% by weight of glass-filled polyamide position), including stabilizers, processing lubricants, etc., without departing from the spirit and scope of the claimed and in the absence of substantial superiority on level operational properties of the obtained polyamide compositions in comparison with the present invention, will be treated as equivalents thereof.

Claims (7)

1. A method of obtaining a glass-filled polyamide composition by extrusion combining polyamide, stabilizer, chopped glass fiber and technological lubricant at a temperature higher than the melting temperature of the polyamide, followed by cooling and granulation of the resulting composition, characterized in that the chopped glass fiber is introduced into the melt of the polyamide in a zone providing length extrusion alignment of the components of the composition from 2 to 16 diameters of the screw of the extruder, in the following ratio of components, wt. %: fiberglass 20.0-55.0 process grease 0.05-1.00 stabilizer 0.02-1.00 aliphatic polyamide the rest is up to 100% 2. A method of producing a glass-filled polyamide composition according to claim 1, characterized in that chopped glass fiber is used in granular and / or dosage form. 3. Glass-filled polyamide composition for the manufacture of structural, electrical and general purpose products, containing aliphatic polyamide, stabilizer, chopped glass fiber and technological lubricant in the following ratio of components, wt. %: fiberglass 20.0-55.0 process grease 0.05-1.00 stabilizer 0.02-1.00 aliphatic polyamide the rest is up to 100% obtained by extrusion alignment of the components of the composition at a temperature exceeding the melting point of the polyamide, at which the chopped glass fiber is introduced into the melt of the polyamide in the zone providing the extrusion alignment length of the components of the composition from 2 to 16 diameters of the screw of the extruder, followed by cooling and granulation of the resulting composition. 4. The glass-filled polyamide composition according to claim 3, characterized in that it further comprises ingredients selected from the group comprising organic, individual, oligomeric, polymeric substances and dispersed inorganic fillers, in an amount up to 7% by weight of the glass-filled polyamide composition.