MXPA00005546A - Moulded parts made from polyoxymethylene having improved resistancy against diesel fuel and agressive engine fuels - Google Patents

Abstract

The use of a thermoplastic molding composition (I) for the production of molded articles (II) having direct contact with diesel or petrol fuel is claimed. (I) comprises:(A) 80-99.8 wt.%of a polyoxymethylenehomo-or copolymer;(B) 0.1-10 wt.%of a polyalkylene glycol;and (C) 0.1-10 wt.%zinc oxide.

Description

PRE-FORMED POLIOXIMETHYLENE PIECE WITH IMPROVED RESISTANCE AGAINST DIESEL FUEL AND GASOLINE CORROSIVE DESCRIPTIVE MEMORY The invention relates to the use of moldable polyoxymethylene material containing polyethylene glycol and zinc oxide for the production of preformed parts, which are used in direct contact with diesel fuel or corrosive gasoline. Polyoxymethylenes (POM) are used, because of their outstanding mechanical properties and good chemical stability, for years in the automobile for many applications. The high stability to fuels in fuel supplying units is especially used. In existing applications, the requirements demanded in the event of a collision must be met in particular, which requires sufficient tenacity of the construction parts. The temperature requirements, which until now persisted in the construction parts of POM in the fuel feed and feedback systems, were at current temperatures up to 60 ° C. In these conditions, the experience of the automotive industry for many years shows that the POM exceeds the requirements imposed.

In the new generations of engines recently developed by the automotive industry, the requirements of stability with respect to temperature at values significantly higher than 100 ° C and above are modified, especially for vehicles driven with diesel fuel. Therefore, also the manufactured parts of POM must meet the increased demands. It turned out, however, that at high temperatures diesel fuel ages and also acts detrimentally in the POM. Thus, for example sulfur or sulfur compounds which are contained in the diesel fuel are oxidized, in the admission of air to acid sulfur compounds, which act disintegratingly in the POM. The damage is recognizable in the specimens due to measurable weight loss and loss of tenacity (for example reduced elongation at break). On the other hand, it is also known that gasoline can age, which can cause aging products. To simulate such aging processes and their influence on construction parts, particularly corrosive gasolines are used in the stability tests, for example in accordance with the standard of E.U.A. SAE J 1681. These fuels generally have a particularly acidic and oxidative character, and can therefore act detrimentally in the POM in the same way as diesel fuels. The construction parts, which are intended for applications with direct contact with fuel, must meet increasingly these higher requirements. Such tests are required in particular in the automotive industry. It was an object of the present invention therefore to discover a moldable polyoxyethylene material, which made it possible to produce construction parts thereof which met the high requirements of stability to diesel fuel and corrosive gasoline. A possibility of improving stability to diesel fuel is mentioned in patent specification DE 197 02 425 A1. The desired improvement is thus achieved by the addition of 0.1 to 2% by weight of at least one sterically hindered amine compound. The present invention presents a completely new method to achieve the desired effect. As additives, they are used in the same ZnO and polyalkylene glycol that causes an additional improvement of the tenacity. The invention relates to the use of a thermoplastic molding material of a mixture of: (A) 80 to 99.8% by weight of a homopolymerized or copolymerized product of polyoxymethylene, (B) 0.1 to 10% by weight of a polyalkylene glycol, (C) 0.1 to 10% by weight of a zinc oxide, resulting in the sum of the percentages by weight of the components (A) to (C) respectively 100%, for the production of preformed parts for applications with direct contact with diesel fuel or gasoline.

According to the invention, the known polyoxyethylene are used as basic polymers (component A), as described in DE-A 2 947 490. These are essentially linear non-branched polymers which generally contain at least 80% by mol, preferably at least 90% by mol of oxymethylene units (-CH 2 O-). The polyoxymethylenes concept also covers both homopolymers of formaldehyde and its cyclic oligomers, such as trioxane or tetroxane and also the corresponding copolymers. The homopolymers of formaldehyde or trioxane are those polymers whose hydroxylene groups are stabilized in a manner known chemically against decomposition, for example by esterification or by etherification. The copolymers are polymers of formaldehyde or a cyclic oligomer, in particular trioxane, and cyclic ethers, cyclic acetals and / or linear polyacetals. Suitable comonomers are cyclic ethers having 3, 4 or 5, preferably 5, 6, 7 or 8 ring members and linear polyacetals. The proportion of the co-components in the polymer is in general from 0.1 to 20% by mole, preferably from 0.5 to 10% by mole. The copolymers are most suitable from 95 to 99.5 mol% trioxane and from 0.5 to 5 mol% of one of the co-components mentioned above. The proportion of the polyoxymethylene in the mixture according to the invention is preferably 95 to 99% by weight.

The polyalkylene glycol preferably has an average molar mass of 10,000 to 45,000. Its proportion in the mixture is preferably from 0.5 to % by weight, particularly preferably 1 to 3% by weight. The polyalkylene glycols are polyethylene glycol and polypropylene glycol, polyethylene glycol is particularly preferred. The proportion of the zinc oxide in the mixture is preferably 0.5 to 5% by weight and particularly preferably 0.5 to 3% by weight. The mixture according to the invention can contain, in the required quantities, additive materials, such as stabilizers, nucleating agents, mold release agents and lubricants, softeners, pigments, dyes, optical brighteners, processing aids and the like. As stabilizers of the polyacetals, polyamides, amides, for example, are suitable, in particular, against the influence of heat. dicyandiamide, hydrazines, ureas, poly- (N-vinyl lactams) and alkaline earth salts of aliphatic carboxylic acids, from mono- to triphasic, preferably containing hydroxy, with 2 to 20 carbon atoms, .gr. calcium stearate, calcium ricinoleate, calcium lactate and calcium citrate. As oxidation stabilizers, biphenol compounds, preferably diesters of monobasic 4-hydroxyphenylalkanoic acids containing from 7 to 13, preferably 7, 8 or 9 carbon atoms, are used.

Suitable light stabilizers are, for example, a-hydroxybenzophenone derivatives and benzotriazole derivatives. The stabilizers are usually employed in a total amount of 0.1 to 5% by weight, in particular in amounts of 0.5 to 3% by weight with respect to the moldable material. Depending on the composition, however, different amounts may also be required. In addition, the mixture according to the invention can also contain filler and reinforcing materials (D). In this case, it can be treated among other things fibrous reinforcing materials, such as glass fibers, carbon fibers, etc., as well as non-fibrous fillers, such as glass powder, graphite, soot, metal powder, metal oxides , silicates, carbonates and molybdenum sulfide (IV). These filling materials may be provided with an adherent agent or a system of adherent agents. The total amount of filler or reinforcer materials (D) is usually up to 50% by weight, preferably from 5 to 40% by weight, with respect to the total mixture of the components (A) - (D). The production of the mixtures according to the invention takes place, for example, by intensively mixing the ingredients at a high temperature, that is to say in general at temperatures above the melting point of component A, namely at approximately 160 and up to 250 ° C, preferably between 180 and 220 ° C in aggregates that mix well, v.gr. in kneaders and extruders, advantageously in extruders of two worms. Usually, the pulverulent components are initially mixed mechanically at room temperature and then remelted until they are completely homogenized. With the use of additive materials, fillers and reinforcers, it can however also be advantageous to use basic mixtures or concentrates thereof. Fibrous materials can also be fed, for example, as a continuous material to the mixture aggregate, in particular to the extruder. The thermoplastic molding materials useful according to the invention are distinguished by a balanced spectrum of properties. Therefore, the preformed parts produced for high temperatures of continuous use up to 100 ° C in contact with diesel fuel as well as for continuous contact with aged or corrosive gasoline. In comparison with the POM molding materials, which do not contain or contain only one of the components (B) and (C), the molding materials according to the invention are characterized by both a reduced chemical decomposition and a reduced loss of properties. mechanical Possible fields of application include, in particular, fuel containers, fuel lines, connection parts, valve bodies, as well as fuel supply units and reservoir pumps. The possible construction parts in the fuel supply units are for example flanges, jet boats, pump supports, fuel pumps, pump covers, filter screens, etc.

EXAMPLES For examples 1, 2, 3 and 4 according to the invention, as well as for comparison example I, the following components were used: Component A Copolymerized product of polyoxymethylene of 98.6% by weight of trioxane and 1.4% by weight of dioxolane. The melting volume regime was 12.5 cm3 / 10 min (190 ° C, 2.16 kg load weight according to ISO 1133).

Component B Polyethylene glycol 35000 P from Clariant GmbH; polyethylene glycol with average molar mass of 35000.

Component C Active zinc oxide® from Bayer AG. The copolymerized POM product was mixed with the parts by weight of the corresponding components according to Table 1 and remelted in a double worm extruder ZE 25 x 33 D (company Berstoff, Hannover, Federal Republic of Germany) at a mass temperature of 200 ° C and granulated below.

The granulated product was dried for eight hours at 120 ° C and then injected into the specimens for storage tests and mechanical tests. The processing conditions were chosen according to the recommendations of ISO 9988-2, material standard for the POM.

Storage and measurements Before storage, five test pieces were weighed to determine their starting weight. In addition, five other test pieces were used as a zero test to determine the mechanical properties in the tensile test. The use of bars for tests of traction of 1/4 of ISO (in the previous ISO 527), which have only 1 mm of thickness, in comparison with the bar for tensile tests type 1A (ISO 527-1, 2) 4 mm thick, it is well-founded because it is found in the smallest measurements of the specimens a significantly greater measuring effect for the decomposition of the material and the mechanical properties. Specimens were stored for 500 h at a temperature of 100 ° C in a glass vessel with reflux cooler and valve for air-tight sealing in test diesel fuel RF 73-A-93 from Haltermann. The volume of the fuel was approximately 2 I and was coated with approximately 1 I of air. A weekly fuel change took place. The specimens are removed after storage and the sticky liquid residues are removed with a cloth. By a second measurement, the change in weight after storage was determined. Subsequently, a tensile test according to ISO 527 with a tensile speed of 12.5 mm / min was carried out with the stored specimens. Table 1 contains the composition of the materials with the corresponding test results.

It is clearly recognizable that the decomposition of material with components B and C is essentially reduced. The best results were achieved with the least possible loss of elongation at break and reduced decomposition of material, with a combination of components B and C.

Claims (5)

NOVELTY OF THE INVENTION CLAIMS

1. - Use of a thermoplastic molding material containing (A) from 80 to 99.8% by weight of a homopolymerized or copolymerized product of polyoxymethylene, (B) from 0.1 to 10% by weight of a polyalkylene glycol, (C) from 0.1 to 10% by weight of a zinc oxide, resulting in the sum of the percentages by weight of components (A), (B) and (C) respectively 100%, for the production of preformed parts for applications with direct contact with diesel fuel or gasoline.

2. Use of moldable materials containing (A) from 30 to 99.8% by weight of a homopolymerized or copolymerized product of polyoxymethylene, (B) from 0.1 to 10% by weight of a polyalkylene glycol, (C) from 0.1 to 10% by weight of a zinc oxide and (D) from 0 to 50% by weight of carriers, reinforcers and / or additives, resulting in the sum of the percentages by weight of the components (A), (B), (C) and (D) respectively 100%, for the production of preformed parts for applications with direct contact with diesel fuel or gasoline.

3. Use according to claim 1 or 2, wherein the polyalkylene glycol has an average molar mass of 10,000 to 45,000.

4. Use according to claim 1 or 2, wherein polyethylene glycol or polypropylene glycol is used as polyalkylene glycol.

5. - Use according to one of claims 1 to 4, wherein in the case of the pre-molded parts are fuel containers, fuel lines, valve bodies, connection parts, fuel supply units and reservoir spouts.