GB2180548A - Mudguards for vehicles - Google Patents

Abstract

The mudguard is made of an ethylene/ alpha -olefin copolymer which may be prepared by copolymerizing ethylene and an alpha -olefin having from 3 to 12 carbon atoms in the presence of a catalyst preferably comprising a solid material containing at least magnesium and titanium and an organic aluminium compound. The copolymer has a melt index of from 0.01 to 100 g/10 min, a density of from 0.860 to 0.910 g/cm<3>, a maximum peak temperature determined by differential scanning calorimetry of not lower than 100 DEG C, and not less than 10 wt% of an insoluble content in boiling n-hexane.

Description

SPECIFICATION Mudgards for vehicles DESCRIPTION The invention relates to a mudguard or flap for a vehicle such an an automobile or bicycle for the prevention of scattering of mud, water or splash by the wheels.

Conventional mudguards are damaged by impinging pebbles or splash, particularly as vehicle speed increased. This tendency is enhanced where roads are in bad condition, and on large-size carrier vehicles. The material for a durable mudguard must have excellent tensile strength, flexing and abrasion resistance, elasticity, heat resistance and oil resistance, and should preserve these properties satisfactorily at low temperature.

A mudguard according to the invention is made of a copolymer of ethylene with an a-olefin having from 3 to 12 preferably from 3 to 6 carbon atoms and the following properties: (a) a melt index of from 0.01 to 100 g/10 min; (b) a density of from 0.860 to 0.910 g/cm3; (c) a maximum peak temperature determined by differential scanning calorimetry (DSC) of not less than 100"C; and (d) not less than 10 wtWo of which is not soluble in boiling n-hexane.

Essential Property (a): The ethylene/a-olefin copolymer should have a melt index Ml (determined in accordance with the JIS Japanese Industrial Standard K-6760 Method) of from 0.01 g/10 min to 100 g/10 min, preferably from 0.1 g/10 min to 50 g/10 min, more preferably 0.5 g/10 min to 20 g/10 min. If the melt index is less than 0.01 g/10 min, the copolymer has poor fluidity, leading to unsatisfactory moulding, so that a mudguard having a uniform thickness cannot be formed. On the other hand, if the melt index of the copolymer is more than 100 g/10 min, the tensile strength of the copolymer is inferior.

Essential Property (b): The ethylene/a-olefin copolymer should have a density (determined in accordance with the JIS K-6760 Method) of from 0.860 to 0.910 g/cm3, preferably from 0.880 to 0.910 g/cm3, more preferably 0.890 to 0.905 g/cm3. If the mudguard is produced using a copolymer having a density of less than 0.860 g/cm3, such a mudguard is too soft and has insufficient strength, with the formation of undesirable sticky surfaces. A copolymer having a density of more than 0.910 g/cm3 is not preferred, since it forms a mudguard which is deficient in resilience or elasticity.

Essential Property (c): The ethylene/a-olefin copolymer should have a maximum peak temperature Tm (determined by differential scanning calorimetry (DSC)) of not less than 100"C, preferably 110 C to 125"C. The maximum peak temperature Tm is a value having a certain relation with the crystal structure. If the Tm of the copolymer is less than 100"C, the product has insufficient heat resistance and tensile strength and the surfaces become sticky.

Essential Property (d): The ethylene/a-olefin copolymer should contain not less than 10 wt%, preferably 30 to 97 wt% which is not soluble in boiling n-hexane. The content which is not soluble in boiling nhexane is a criterion showing the content of amorphous material and the content of oligomers.

When the insoluble content is less than 10 wt%, the contents of amorphous material and oligomers are increased so that the strength of the product is lowered, the surfaces become sticky, attract dust, and integrity is difficult to preserve.

The maximum peak temperature is determined by the following DSC: About 5 mg of a sample is cut from a 100 micron thick film prepared by hot press moulding, the sample is weighed accurately, and put into apparatus for the DSC. After maintaining the sample at 1700C for 15 minutes, the temperature is lowered at a rate of 2.5"C/min to 0 C. Thereafter, the temperature is raised at a rate of 10 C/min until it reaches 170"C. The temperature at which the maximum peak is observed is the maximum peak temperature Tm.

The content which is insoluble in boiling n-hexane is determined as follows. A 200 micron thick sheet is moulded using a hot press. Three 20 mmX30 mm pieces are cut off from the sheet, and each is put into a double-tube Soxhlet extractor and is subjected to extraction with boiling n-hexane for 5 hours. The content which is not dissolved in boiling n-hexane is removed from the extractor, dried in vacuum at 50"C for 7 hours, and weighed. The content which is insoluble in boiling n-hexane is calculated from the following equation.

In soluble content in boiling n-hexane Weight of sheet piece after extraction X 100 (wt%) Weight of sheet piece before extraction Specific examples of a-olefins suitable for copolymerization with ethylene include propylene, butene-1, 4-methylpentene-1, hexene-1, octene-1, decene-1 and dodecene-1. Particularly preferred are propylene, butene-1, 4-methylpentene-1 and hexene-1. The content of a-olefin in the ethylene/a-olefin copolymer is preferably from 5 to 40 mol%.

The catalyst system used in the preparation of the copolymer is preferably a combination of a solid material containing at least magnesium and titanium, and an organo aluminium compound.

The solid material preferably comprises a magnesium-containing inorganic solid carrier and a titanium compound carried thereby. Examples of the carrier are metallic magnesium, magnesium hydroxide, magnesium carbonate, magnesium oxide and magnesium chloride; and complex oxides, carbonate, chloride and hydroxides of magnesium with one or more of silicon, aluminium and calcium.

The carrier may be treated or reacted with an oxygen-containing compound, sulphur-containing compound, an aromatic hydrocarbon or a halogen-containing compound. Example of suitable oxygen-containing compounds include inorganic and organic oxygen-containing compounds, such as water, alcohols, phenols, ketones, aldehydes, carboxylic acids, esters, polysiloxane, acid amines, metal alkoxides and metal oxychlorides. Examples of suitable sulphur-containing compounds include organic sulphur-containing compounds, such as thiols and thioethers, and inorganic sulphur-containing compounds, such as sulphur dioxide, sulphur trioxide and sulphuric acid.

Examples of suitable aromatic hydrocarbon include monocyclic or polycyclic aromatic hydrocarbons, such as benzene, toluene, xylene, anthracene and phenanthrene. Examples of suitable halogen-containing compounds include chlorine, hydrogen chloride, metal chlorides and halogen containing organic compounds.

Examples of suitable titanium compounds include halides, alkoxyhalides, alkoxides and halogenated oxides of titanium. Titanium compounds containing tetravalent or trivalent titanium may be used. Examples of titanium compounds containing tetravalent titanium preferably used may be represented by the general formula of Ti(OR)"X4 n wherein R is an alkyl, aryl or aralkyl group having from 1 to 20 carbon atoms, X is a halogen atom and n stands for 0 < n < 4. Specific examples of such titanium compounds are titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, monomethoxytrichlorotitanium, dimethoxydichlorotitanium, trimethoxymonochlorotitanium, tetramethoxytitanium, monoethoxytrichlorotitanium, diethoxydichlorotitanium, triethoxymonochlorotitanium, tetraethoxytitanium, monoisopropoxytrichlorotitanium, diisopropoxydichlorotitanium, triisopropoxymonochlorotitanium, tetraisopropoxytitanium, monobutoxytrichlorotitanium, dibutyoxydichlorotitanium, monopentoxytrichlorotitanium, monophenoxytrichlorotitanium, diphenoxydichlorotitanium, triphenoxymonochlorotitanium and tetraphenoxytitanium.

Suitable titanium trihalides may be prepared by reducing titanium tetrahalides, such as titanium tetrachloride or titanium tetrabromide, with hydrogen, aluminium or an organo compound of a metal of Groups I to Ill of the Periodic Table. Other examples of compounds containing trivalent titanium are those which may be prepared by reducing halides of alkoxytitanium in a tetravalent state represented by the general formula of Ti(OR),nX4 m where R is an alkyl, aryl or aralkyl group having from 1 to 20 carbon atoms and m stands for 0 < m < 4, with an organo compound of a metal of Groups I to Ill of the Periodic Table.

To prepare a catalyst system, an organo aluminium compound may be combined with a solid material which contains catalyst components. Examples of such solid material are MgO-RX-TiCI4 (disclosed by Japanese Patent Publication No. 3514/1976), Mg-SiCI4-ROH-TiCI4 (disclosed by Japanese Patent Publication NO. 23864/1975), MgCI2-Al(OR)3-TiCI4 (disclosed by Japanese Patent Publication Nos 152/1976 and 15111/1977), MgCI2SiCI4-ROH-TiCI4 (disclosed by Japanese Patent Laid-Open Publication No. 106581/1974), Mg(OOCR)2-Al(OR)3-TiCI4 (disclosed by Japanese Patent Publication No. 11710/1977), Mg-POCI3-TiCI4 (disclosed by Japanese Patent Publication No. 153/1976), MgCI2-AIOCI-TiCI4 (disclosed by Japanese Patent Publication No.

15316/1979, and MgCI2Al(ORnX3n-Si(OR')mX4m-TiCi4 (disclosed by Japanese Patent Laid-Open Publication No. 95909/1981). In the above formulae, R and R' are organic residues and X is a halogen atom.

Alternatively, a catalyst may be prepared by combining an organo aluminium compound with a reaction product of an organo magnesium compound, such as a Grignard compound, and a titanium compound. Examples of the organo magnesium compound are those of the general formulae RMgX, R2Mg and RMg(OR), wherein R is an organic residue having 1 to 20 carbon atoms and X is a halogen atom; complexes of ethers with the aforementioned organo magnesium compounds; and modified products of the aforementioned organo magnesium compounds prepared by mixing with other organo metal compounds, such as organo sodium compounds, organo lithium compounds, organo potassium compounds, organo boron compounds, organo calicium compounds and organo zinc compounds.

The catalyst may be prepared, for example, by combining an organo aluminium compound with RMgX-TiCI4 (disclosed by Japanese Patent Publication No. 12953/1979), RMgX-halogenated phenol-TiCI4 (disclosed by Japanese Patent Publication No. 12954/1979) or RMgX-CO 2 TiCI4 (disclosed by Japanese Patent Publication No. 73009/19821.

Further examples are combinations comprising an organo aluminium compound and a solid material which is prepared by contacting an inorganic oxide, such as SiO2 or Awl203, with the aforementioned solid catalyst component containing at least magnesium and titanium. Usable inorganic oxides, other than SiO2 and Awl203, include CaO, B203 and SnO2. Double oxides of the aforementioned inorganic oxides may also be used. Each of the aforementioned inorganic oxides or double oxides may be contacted with the solid catalyst component containing at least magnesium and titanium by a conventional method.For example, a desired inorganic oxide may be reacted with a selected solid catalyst component containing at least magnesium and titanium in the presence or absence of an inert solvent, preferably, at from 50 to 300"C for from 5 minutes to 20 hours. Alternatively, the former may be pulverized together with the latter. Both of the aforementioned methods may be combined to react the inorganic oxide with the solid catalyst component.

The catalyst may be prepared by combining an organo aluminium compound with SiO2-ROH-MgCI2-TiCI4 (disclosed by Japanese Patent Laid-Open Publication No. 47407/1981), SiO2-R-O-R'-MgO-AICI3-TiCI4 (disclosed by Japanese Patent Laid-Open Publication No.

187305/1982) or SiO-MgCI2-Al(OR)3-TiCl4-Si(OR')4 (disclosed by Japanese Patent Laid-Open Publication No. 21405/1983). In the above formulae, R and R' are hydrocarbon residues.

The titanium compound may be in the form of an addition product with an organic carboxylic ester. The inorganic solid compound containing magnesium may be used after it is treated with an organic carboxylic ester. Similarly, an organo aluminium compound may be used in the form of an addition prodcut with an organic carboxylic ester. Examples include various aliphatic, alicyclic and aromatic carboxylic esters, those having 7 to 12 carbon atoms being preferred.

Specific examples are alkyl (such as methyl and ethyl) esters of benzoic acid, anisic acid and toluic acid.

Examples of preferred organo aluminium compounds include organio aluminium compounds of the general formulae R3AI, R2AIX, RAIX2, R2AIOR, RAI(OR)X or R3AI2X3, wherein R is a same or different group and stands for an alkyl, aryl or aralkyl group, and X is a halogen atom. Specific examples are triethylabuminium, triisobutylaluminium, trihexylaluminium, trioctylaluminium, diethylaluminium chloride, diethylaluminium ethoxide, ethylaluminium sesquichloride and mixtures of two or more thereof. The amount of the organo aluminium compound used is not critical; from 0.1 to 1000 mols per mol of the titanium compound may be used.

The catalyst may be contacted with an a-olefin prior to the polymerization step to improve the subsequent polymerization activity and to stabilize the polymerization reaction. Various a-olefins may be used for this purpose, the preferred being a-olefins having from 3 to 6 or 8 carbon atoms. Examples of preferred a-olefins are propylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, decene-1, dodecene-1 and mixtures thereof. The reaction conditions for contacting the catalyst system with a selected a-olefin may be within wide ranges. For example, the catalyt system may contacted with a-olefin at from 0 to 200"C, preferably at from 0 to 110"C, for from one minute to 24 hours. The amount of a-olefin added to the catalyst system may be within a wide range.It is desired that one gram of the solid catalyst components may be treated generally with 1 to 50,000 grams, preferably 5 to 30,000 grams, of an a-olefin so that 1 to 500 grams of the a-olefin is reacted per gram of the solid catalyst component. The pressure during this contact may be selected freely, but is desirably from -(minus) 1 kg/cm2 G to 100 kg/cm2 G.

When the solid catalyst component is treated with an a-olefin, all of the organo aluminium compound to be used may be combined with the catalyst component, and then contacted with the a-olefin, or a part of the organo aluminium compound to be used may be combined with the solid catalyst component and then contacted with the a-olefin. The residue of the organo aluminium compound may separately be added to the reaction system at the subsequent poly merization step. Hydrogen gas or an inert gas, such as nitrogen, argon or helium, may be present on the contacting the catalyst with the a-olefin.

The polymerization can be effected in the same way as polymerization where a Ziegler catalyst is used. The polymerization proceeds substantially in the absence of oxygen and water in a vapour phase or in the presence of an inert solvent, or by utilizing the monomer per se as the solvent. The polymerization may be carried out at from 20 to 3000C, preferably from 40 to 200"C, and at a pressure of from atmospheric to 70 kg/cm2 .G, preferably from 2 kg/cm2 .G to 60 kg/cm2 .G. Although the molecular weight of the copolymer may be controlled by varying the conditions for the polymerization reaction, for example the polymerization temperature or the molar ratio of the catalysts. To some extent, molecular weight control can be effected by addition of hydrogen.Polymerization may be performed in two or more reaction stages, the hydrogen temperature, the polymerization temperature or other reaction conditions being variable at every stage.

The ethyleneja-olefin copolymer may be admixed with one or more other olefin polymers so long as the properties do not deteriorate. Examples of such olefin polymers are high pressure process polyethylenes, ethylene/vinyl acetate copolymers, linear low density polyethylenes, propylene/butene-1 copolymers, stryrene/butadiene block copolymers and olefinic or other thermoplastic elastomers. Preferably these polymers are admixed with the copolymer in the ratio of not more than 100 parts by weight per 100 parts of copolymer. The copolymer may be mixed with one or more additives, such as stabilizers, antioxidants, ultra-violet ray absorbing agents, foaming agents, antistatic agents, flame retarding agents, dyes, pigments, talc, calcium carbonate, carbon black, silica and various fibres or other fillers.In this connection, the copolymers have an advantage that the additives can safely be used in a high proportion.

The mudguard of the invention may be made entirely of copolymer, or the copolymer may be combined with a reinforcing material, such as woven or nonwoven cloth, to form a laminate. By laminating with a reinforcing material, the strength is increased. The mudguard may be moulded by injection moulding, extrusion moulding and various other moulding processes. When a mudguard is made of a mixture of the enthylene/a-olefin copolymer with one or more additives, the mixture is kneaded before moulding. A laminated mudguard may be prepared by hot pressing a sheet of the copolymer on a sheet of the reinforcing material. Otherwise, the ethylene/a-olefin copolymer or a mixture containing the same may be melted, and the molten mass thereof presses on and into a sheet of the reinforcing material using a calender roller.

The thickness of the mudguard is left to the discretion of a person having ordinary skill in the art as a design matter, the prefered thickness being from 0.5 to 10 mm. The surface of the mudguard may be embossed or printed.

In the following Examples, sample sheets are prepared and tested thus: Preparation of Sample Sheet Each of the compositions was put into a mould having a dimensions of 2mmX150mmX150mm, preheated at 210 C for 5 minutes, moulded at 2100C while applying a pressure of 150 kg/cm2 for 5 minutes, and then cooled to 30"C and maintained at 30"C for 10 minutes at a pressure of 150 kg/cm2. The moulded sheet was removed from the mould annealed at 50"C for 20 hours, kept at room temperature for 24 hours, and then subjected to tests.

Tensile Strength In accordance with the JIS K-6301 Method, a test piece was prepared using No. 3 Dumbbell specimen, and the tensile strength of the test piece was measured at a pulling speed of 50 mm/min.

Hardness A test piece was prepared in accordance with the JIS K-6301 Method, and the hardness was measured using a C-type tester.

Flex Test A test piece was prepared in accordance with the JIS K-6301 Method, and subjected to repeated bending while using a De Mattia flex testing machine.

Resistance to Oil A test piece was prepared in accordance with the JIS K-6301 Method, and dipped in the JIS No. 3 oil at 23"C for 22 hours, the percent change in volume being determined.

EXAMPLE 1 A solid catalyst component prepared from substantially anhydrous magnesium chloride, 1,2dichloroethane and titanium tetrachloride was combined with triethylaluminium. Ethylene and butene-1 were copolymerized to obtain an ethylene/butene-1 copolymer. The content of ethylene in the copolymer was 87.9 mol%. The copolymer had a melt index of 1.0 g/10 min, a density of 0.895 g/cm3, a maximum peak temperature of 119"C, and contained 72 wt% of insolubles in boiling n-hexane. Its properties are in Table 1.

EXAMPLE 2 Using the same catalyst as used in Example 1, an ethylene/butene-1 copolymer was prepared.

The content of ethylene was 91.0 mol%. The copolymer had a melt index of 5.1 g/10 min, and density of 0.903 g/cm3, a maximum peak temperature of 121"C, and contained 78 wt% of insolubles in boiling n-hexane. Its properties are in Table 1.

EXAMPLE 3 A solid catalyst components prepared from substantially anhydrous magnesium chloride, anthracene and titanium tetrachloride was combined with triethylalumunium. Ethylene and propylene were copolymerized thereon.

The content of ethylene in the copolymer was 88.0 mol%. The copolymer has a melt index of 1.0 g/10 min, a density of 0.901 g/cm3, a maximum peak temperature of 121"C, and contained 79 wt% of insolubles. Its properties are in Table 1.

EXAMPLE 4 100 parts by weight of the ethylene/butene-1 copolymer prepared in Example 1 was blended with 5 parts by weight of carbon black. Using an extruder provided with a T-die, a sheet having a thickness of 1.5 mm, a width of 60 cm and a length of 90 cm was moulded from the blend.

The sheet was attached to a large-sized truck to cover rear wheels as mudguards. At the time after the cruising distance of the truck reached about 50,000 km, the mudguard was inspected thoroughly. The result was that no serious damage was found and the mudguard was still in a satisfactory condition.

Table 1 : Properties

MI Density Tm Insoluble Tensile Blongation Hardnese Flex Percentage Example g/10 min g/cm C Content Strangth % JIS C Test Change in in boiling kg/cm (times) Volume n-Hexane (23 C x 22hr) (wt%) 1 1.0 0.895 119 72 180 910 59 > 10,000 49 2 5.1 0.903 121 78 140 1000 65 4,000 49 3 1.0 0.901 121 79 120 900 60 4,500 46

Claims (12)

1. A mudguard for a vehicle being made of copolymer of ethylene with an a-olefin having from 3 to 12 preferably from 3 to 6 carbon atoms and the following properties: (a) a melt index of from 0.01 to 100 g/10 min; (b) a density of from 0.860 to 0.910 g/cm3; (c) a maximum peak temperature determined by differential scanning calorimetry (DSC) of not less than 100"C; and (d) not less than 10 wt% of which is not soluble in boiling n-hexane.

2. A mudguard according to claim 1 wherein the a-olefin has from 3 to 6 carbon atoms.

3. A mudguard according to claim 1 wherein the a-olefin is propylene, butene-1, 4-methyl pentene-1, hexene-1, octene-1, decene-1 or dodecene-1.

4. A mudguard according to any preceding claim in which the copolymer is prepared to copolymerizing in the presence of a catalyst comprising solid material containing at least magnesium and titanium.

5. A mudguard according to claim 4 in which the solid catalyst component is of the general formula MgO-RX-TiCI4, MgSiCI4-ROH-TiCI4, MgCI2-Al(OR)3-TiCl4, MgCl2-SiCI4-ROH-TiCI4, Mg(OOCR)2-AI(OR)3-TiCl4, Mg-POCl3-TiCI4, MgCl2-AlOCl-TiCl4, or MgCI2-Al(OR)nX3.n-Si(OR')mX4 m-TiCI4, R and R' being organic residues and X a halogen atom.

6. A mudguard according to claim 4 in which the solid catalyst component is of the general formula RMgX-TiCI4, RMgX-phenol-TiCI4, RMgX-halogenated phenol-TiCI4, or RMgX-CO2-TiCI4, R being an organic residue and X a halogen atom.

7. A mudguard according to claim 4 in which the solid catalyst compoent is of the general formula SiO2-ROH-MgCl2-TiCI4, SiO2-R-O-R'-MgO-AlCI3-TiCl4 or SiO2MSiO2MgCl2-AI(OR)3--Ti- Cl4-Si(OR')4, R and R' being hydrocarbon residues.

8. Mudguard according to claim 4 in which the catalyst contains one or more organo aluminium compounds of the general formulae of R3AI, R2AIX, RAIX2, R2AIOR, RAI(OR)X and R3AI2X3, each R being an alkyl, aryl or aralkyl group (the same or different) and X being a halogen atom.

9. A mudguard according to claim 8 in which the organo aluminium compound is triethylaluminium, triisobutylaluminium, trihexylaluminium, trioctylaluminium, diethylaluminium chloride, diethylaluminium ethoxide, ethylaluminium sesquichloride or a mixture of two or more thereof.

10. A mudguard according to any preceding claim in which the copolymer is admixed with one or more high pressure process polyethylenes, ethylene/vinyl acetate copolymers, linear low density polyethylenes, propylene/butene-1 copolymers, styrene/butadiene block copolymer and olefinic thermoplastic elastomers, in a ratio of not more than 100 parts by weight per 100 parts of copolymer.

11. A mudguard according to any preceding claim in which the copolymer is laminated with a reinforcing substrate material.

12. A mudugard for a vehicle made of a copolymer produced substantially as herein described in any of the Examples.