EP0289996B1 - Process for the production of a hydrophilic coating on a moulded part, and razor manufactured by applying the process - Google Patents

Abstract

A process for forming and applying a hydrophilic coating which has very low friction in the moist state to a razor, in which a solution containing a water-soluble polymer, in particular polyvinylpyrrolidone, is applied and cured. The razor is made of plastic, such as polystyrene or ABS, or of metal provided with a device which reduces the friction. The invention proposes that the solution applied to the moulding comprises a water-soluble polymer, in particular poly-N-vinylpyrrolidone or a copolymer thereof, one or more free radical-polymerisable vinylmonomers and a photoinitiator which decomposes on irradiation to form free radicals, and that the applied solution is exposed to UV irradiation for curing.

Description

The invention relates to a process for the formation and application of a hydrophilic coating which is highly lubricious in the moist state on a molded part made of plastic or metal, in particular a razor or razor blade unit, in which a solution containing a water-soluble polymer, in particular polyvinylpyrrolidone, is applied to the molded part and cured there becomes. The invention further relates to a razor or a razor blade unit with at least one razor blade held on a blade support and a surface adjacent to the razor blade that sweeps over the skin of the user during the shaving process, in particular a cap made of plastic, such as polystyrene or ABS, or of metal that is coated with a the lubricity-increasing device is provided.

From DE-OS 28 51 457 a razor made of plastic is known, in which at least one razor blade is arranged between a razor blade support and a cap. The shaver head has an integral solid and water soluble shaving aid. The shaving aid is provided in the form of a strip made of the solid but water-soluble material, the strip being arranged in an adjacent position to the razor blade and being attached either to the blade support or to the cap. In particular is a microencapsulated silicone oil, polyethylene oxide, a nonionic polyacrylamide or a polysaccharide is provided as the water-soluble material. This is to achieve a perfect wet shave in that the shaving aid in contact with damp skin or, if necessary, by moistening the shaver head itself and immediately after each shaving process is applied to the skin again, so that it with its sliding properties continuously during the duration of the Shaving works.

A disadvantage of the known razor is that the substance acting as a lubricant detaches from the carrier body and is deposited on the skin of the user in the form of a film. There is thus the risk of causing skin irritation, as well as the need to rinse off the lubricating film that dries on already shaved skin, which can be difficult depending on the hardness of the water available. In addition, the construction of the razor with a plastic strip arranged in a recess is complex and it is not possible to move the strip into the actual vicinity of the cutting edge of the razor blade. In principle, therefore, the known sliding strip is only to be positioned at a location on the shaving apparatus which is unfavorable for the desired use properties.

From DE-PS 28 28 617 a molded body made of a polymeric substrate and a coating layer applied to this substrate is also known, in which it consists of a polyvinylpyrrolidone-polyurethane interpolymer. Various applications, such as contact lenses, catheters, peristaltic pump chambers, condoms and the like, are mentioned for such a shaped body, in which it is desirable to use a material, such as polyurethane, an acrylic acid polyester or a vinyl resin, which has a lower content in the moist state Has a coefficient of friction that is otherwise the case with such materials is possible. Unlike in medical technology, such requirements do not exist with conventional shavers and it is also not common to use such materials, in particular a polyurethane. Rather, the razors and razor blade unit are made of polystyrene, the properties of which are not comparable. In particular, a coating applied by the process according to DE-PS 28 28 617 would not adhere to polystyrene. It is namely proposed there that a solution of a polyisocyanate is applied to the substrate and, after the solvent has evaporated, a solution of polyvinylpyrrolidone is applied to the substrate treated in this way, after which the solvent is evaporated to give a polyvinylpyrrolidone-polyurethane interpolymer. Another disadvantage of this process is that the formation of a coating layer in this way is a time-consuming process, since the individual components are applied from dilute solutions, the solvents are slowly evaporated and free isocyanate groups are reacted at elevated temperature. If this complicated process were to be applied to the manufacture of razors, there would be a risk of stress cracks or deformation processes. Finally, this method is not transferable to the manufacture of shavers because the solutions consist only of about 10 to 15% of substances that do not evaporate during the manufacturing process, so that only extremely thin layers can be achieved for the sliding coating. The layer thicknesses are also extremely difficult to control and it is at least difficult to apply to round surfaces. The control of the curing process by evaporation must also be carried out very slowly and carefully so that the process runs from the inside out and to avoid undesired substances being trapped in the end product. that would come off during the shaving process and would remain on the skin.

The invention has for its object to improve a method of the type mentioned while avoiding the above disadvantages in such a way that the production of molded parts made of plastic or metal, in particular razors or razor blade units or their parts, high lubricity is made possible in the moist state, the The coating also adheres well to polystyrene or ABS or metal and should be applied and hardened in a short time. In particular, the invention is based on the objective of improving the sliding properties of a razor, particularly in the area close to the blade, in a way which prevents substances in the manner of a lubricant from depositing on the skin of the user.

The object is achieved according to the invention in that the solution to be applied to the molded part consists of the water-soluble polymer, in particular poly-N-vinylpyrrolidone or a copolymer thereof, one or more radically polymerizable vinyl monomers and a photoinitiator which decomposes into free radicals when irradiated and that the applied one Solution for curing is exposed to UV radiation. The solution then hardens quickly to a well-adhering coating of controlled layer thickness, which has a greatly reduced coefficient of friction in contact with skin when wet. The solution preferably contains 0.1 to 90% by weight of polyvinylpyrrolidone, in particular 5 to 30% by weight of polyvinylpyrrolidone, based on the vinyl monomers used. The average molecular weight of polyvinylpyrrolidone can be different values from 15,000 to 800,000 g / mol, preferably 200,000 to 500,000 g / mol.

Instead of using pure polyvinylpyrrolidone, which is particularly suitable, copolymers of pyrrolidone with, for example, maleinates or acrylates in the sense of the invention can also be used. Other water-soluble polymers, such as polyvinyl alcohol, polymers containing polyacrylamide, polysaccharides or polyethylene oxide, are also suitable as additives.

Radically polymerizable vinyl monomers suitable for the purposes of the invention are preferably acrylic acid, methacrylic acid and their derivatives and mixtures of styrene and maleic acid or fumaric acid-containing polyester resins. Examples are cyclic or open-chain ether groups containing acrylic acid esters or methacrylic acid esters, such as esters of mono- or poly-ethoxylated or propoxylated C₁ - C₂en alcohols, THF-carbinol acrylate or THF-carbinol methacrylate, hydroxyalkyl esters, such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate Hydroxypropyl methacrylate, N, N-dimethylamino-2-hydroxyethyl acrylate, N, N-dimethylaminoethyl metharylate or salts thereof, such as N, N, N-trimethylammonium-2-ethyl methyl acrylate chloride, furthermore acrylamide, N-alkylacrylamide with 1-10 C atoms in the alkyl group, N-2-hydroxyethylacrylamide, N-2-hydroxypropylacrylamide or methacrylamide, N-2-hydroxyethyl methacrylamide, N-2-hydroxypropyl methacrylamide, acrylonitrile and methacrylonitrile.

The also suitable polyester resin systems contain maleic acid or fumaric acid and z. B. phthalic acid, adipic acid, sebacic acid and hydrophilic polyetherdiols, such as diethylene glycol, oligoethylene glycol with 3 - 1,000 ethylene oxide units, oligopropylene glycol with 1 - 1,000 propylene oxide units, furthermore ethylene glycol, butanediol, trimethylolpropane or ethoxylated trimethylolpropane with 3 - 60 ethylene oxide / propanols and propoxylated or ethoxylated and ethoxylated 0 - 60 parts of propylene oxide.

The hydrophilic vinyl monomer mixtures preferably contain from 0 to 80% by weight, in particular 0.5 to 50% by weight, of hydrophobic monomers, such as methyl methacrylate, butyl acrylate, ethyl acrylate, cyclohexyl acrylate or ethyl hexyl acrylate. Urethane-modified acrylic and methacrylic esters can also be used, which in a known manner, for. B. by the reaction of 2-isocyanatoethyl methacrylate with various C₁ to C₆ alcohols, especially methanol, ethanol or butanol, alkoxy alcohols, such as ethoxylated and / or propoxylated methyl, ethyl, propyl, butyl or hexyl or. Ethylhexyl alcohol, or by reacting hydroxyalkyl acrylates or hydroxyalkyl methacrylates with aromatic or aliphatic mono-, di- or triisocyanates such as hexamethylene diisocyanate, lysine methyl ester diisocyanate, toluene diisocyanate, MDI diphenylmethane diisocyanate or an adduct of trimethylol propane and 3 mol toluene diol. Furthermore, N-vinylpyrrolidone can be used in the hydrophilic vinyl monomer mixture, which is particularly suitable as an additive in the sense of the invention.

Although polyfunctional vinyl compounds are not absolutely necessary in the sense of the invention, the addition in an amount of 0 to 80% by weight, preferably up to 50% by weight, likewise leads to qualitatively good results. Suitable crosslinking components are, for example, butanediol bisacrylate, 1,6-hexanediol bisacrylate, oligoethylene glycol bisacrylates with 1 to 400 ethylene glycol units, acrylates or methacrylates of trimethylolpropane, ethoxylated and / or propoxylated trimethylolpropane. Bis (2-hydroxyethyl) bisphenol A dimethacrylate or an adduct of (meth) acrylic acid and bisphenol A diglycidyl ether or urethane-modified bisacrylates is also suitable.

The mixtures mentioned to be applied to the molded part can be produced with a solvent which has a favorable effect on the processability of the system. Suitable solvents are acetone, methyl ethyl ketone, methanol, ethanol, propanol, butanol, ethyl acetate, butyl acetate, methylene chloride, toluene, THF, water and mixtures thereof.

Photoinitiators can be used in the vinyl monomer mixture in an effective amount of 0.01 to 5% by weight, in particular 0.1 to 5% by weight and preferably in an amount of 0.3 to 1% by weight. Compounds are used that break down into radicals due to UV radiation. Effective photoinitiators are, for example, the known compounds benzophenone, acetophenone, fluorenone, benzaldehyde, propiophenone, anthraquinone, carbazole, 3- or 4-methylacetophenone, 3- or 4-methoxybenzophenone, 4,4'-dimethoxybenzophenone, allylacetophenone, 2,2'-diphenoxy , Benzoin, methyl benzoin ether, ethyl benzoin ether, propyl benzoin ether, benzoin acetate, benzoin phenyl carbamate, benzoin acrylate, benzoin phenyl ether, benzoyl peroxide, dicumyl peroxide, azoisobutyronitrile, phenyl disulfide, acylphosphine oxides or chloromethylanthraquinone and mixtures thereof.

In addition to the photoinitator, 0.3 to 5.0% by weight of an activator can also be mixed into the coating system. Suitable activators are, for example, mercaptoacetic acid, organic amines, such as n-decylamine, piperazine, morpholine, tributylamine, benzylamine, allylamine, polyethyleneimine and / or piperidine.

The razor or razor blade unit according to the invention is characterized in that the lubricity-increasing device comprises a 5 to 1,000 µm thick layer of a mixture of water-soluble polymers, in particular poly-N-vinylpyrrolidone or a copolymer thereof, cured by UV radiation, or one or more radicals polymerizable vinyl monomers and a photoinitiator which decomposes into free radicals when irradiated. Further configurations of this lubricity layer result from the compositions listed above. The special advantage is that the coating of the shaver, razor head or the razor blade unit can take place over a large area, even over the entire area, on the polystyrene or ABS or metal carrier body or PVC film to be subsequently glued on, the layer thickness being adjustable very well so that the volume of the solution applied does not change during the curing process, so that the applied layer thickness is retained. By adjusting the viscosity of the solution, it is also possible to form relatively thick layers without the solution running away uncontrollably after application and thus causing a change in layer thickness. The layer also adheres extremely well to polystyrene or ABS, which is generally used as a molded plastic body on razors, but also to metal surfaces, so that the formation of the sliding layer is simple.

Further details, features and advantages of the subject matter of the invention result from the following description of the associated examples and the drawing, in which a shaving apparatus according to the invention is shown schematically.

example 1

A mixture of 2.40 g of tetrahydrofuranyl 2-methyl acrylate, 0.05 g of photoinitiator (Darocur 1116, Merck), 0.25 g of polyvinylpyrrolidone and 0.05 g of tetraethylene glycol diacrylate is applied to a polystyrene support with a brush and then the top layer irradiated with an 80 W UV lamp at a distance of 5 cm for 15 min. When cured, the hardened coating has a drastically reduced frictional resistance. Sliding friction of a leather disc, which is pressed onto the coated surface with 1 kg / 8 cm²:
dry 350 CN
Wet 180 CN

Example 2

A mixture of 2.45 g of tetrahydrofuranyl-2-methyl acrylate, 0.05 g of photoinitiator (Darocur 1116), 0.25 g of polyvinylpyrrolidone is applied to a polystyrene body with a sponge and then with an Hg UV lamp at a distance of 30 min Irradiated 10 cm. The hardened coating shows a drastically reduced coefficient of friction when wet. Sliding friction of a leather disc, which is pressed 1 kg / 8 cm² pressure on the treated and hardened surface:
dry 360 CN
wet 200 CN

Example 3

2.30 g of tetrahydrofuranyl-2-methyl acrylate, 0.20 g of photoinitiator and 0.25 g of polyvinylpyrrolidone are mixed, applied to a polystyrene support with a roller and then cured with an 80 W UV lamp at a distance of 5 cm for 15 min. The frictional resistance of the coated surface is greatly reduced by moistening. Sliding friction of a leather disc which is pressed onto the hardened surface with 1 kg / 8 cm² pressure:
dry 350 CN
wet 210 CN

Example 4

10 g of N-vinylpyrrolidone, 10 g of trimethylolpropane monoacrylate (Roskydal KL 5-2475, Bayer) are mixed with 4 g of PVP and 0.75 g of photoinitiator (Darucur 1116, Merck), using a doctor blade on an ABS or foil support made of PVC and irradiated at a distance of 5 cm with an 80 W UV lamp for 3 min.

A surface which is highly slidable when wet is obtained.
Coefficient of friction dry 330 CN
Coefficient of friction wet 80 CN

Example 5

5 g of NVP, 5 g of trimethylolpropane monoacrylate are mixed with 2 g of PVP and 0.18 g of photoinitiator (Lucirin LR 8728, BASF), applied to a carrier made of ABS or a film made of PVC using a doctor blade and at a distance of 5 cm using a 80 W UV lamp irradiated for 45 sec.

A surface is also obtained whose frictional resistance is drastically reduced by moistening.
dry 340 CN
wet 100 CN

The razor 1 shown in perspective in the single figure of the drawing has a razor blade unit 3 which can be placed on a handle and in which two razor blades 4, 5 are fixedly arranged between a raiser blade carrier 6 and a cap 7 in a conventional manner. A protective and guide bar 8 is arranged on the razor blade carrier and is ribbed in the usual way. The entire cap 7 and possibly the guide surface is provided with a sliding layer 2 shown hatched in the drawing, which has been applied according to one of the above examples 1 to 3 and consists of the preferred mixtures of substances mentioned.

Claims (11)

1. A process for forming and applying a hydrophilic coating which, in the damp state, is highly slidable, to a plastic or metal moulding directly or indirectly via a plastic film, more particularly a razor or razor blade unit, in which process a solution containing a water-soluble polymer, more particularly polyvinylpyrrolidone is applied to the moulding and cured there, characterised in that the solution applied to the moulding consists of the water-soluble polymer, more particularly poly-N-vinylpyrrolidone or a copolymer thereof, one or more radically polymerisable vinyl monomers and a photoinitiator which decomposes into radicals on irradiation, and in that the applied solution is exposed to an UV-irradiation for curing purposes.
2. A process according to claim 1, characterised in that the solution contains 0. 1 to 90% by weight of polyvinylpyrrolidone, preferably 5 to 30% by weight of polyvinylpyrrolidone.
3. A process according to claim 2, characterised in that the average molecular weight of the polyvinylpyrrolidone is 200 000 to 500 000 g/mol.
4. A process according to any one of claims 1 to 3, characterised in that the vinylmonomers used are acrylic acid, methacrylic acid and their derivatives and mixtures of acrylic acid derivatives with N-vinylpyrrolidone and mixtures of polyester resins containing styrene and maleic acid or fumaric acid.
5. A process according to any one of claims 1 to 4, chracterised in that the vinylmonomer mixtures have proportions of 0 to 80% by weight, preferably 0.5 to 50% by weight, of hydrophobic monomer, such as methyl methacrylate, butylacrylate, ethylacrylate, cyclohexylacrylate or ethyl-hexylacrylate.
6. A process according to any one of claims 1 to 4, characterised in that the vinyl monomers are urethane-modified acrylic or methacrylic esters.
7. A process according to any one of claims 1 to 6, characterised in that multi-functional vinyl compounds are added in a quantity of up to 50% by weight.
8. A process according to any one of claims 1 to 7, characterised in that the solvents used for the solution to be applied are acetone, methylethylketone, methanol, ethanol, propanol, butanol, ethylacetate, butylacetate, methylene chloride, toluene, THF or water and mixtures thereof.
9. A process according to any one of claims 1 to 8, characterised in that the photo-initiator is used in the solution in a quantity of from 0.01 to 5% by weight, preferably 0.3 to 5% by weight.
10. A process according to claim 9, characterised in that 0.3 to 5% by weight of a photo-activtor, more particularly mecaptoacetic acid and/or organic amines, are additionally added to the solution.
11. A razor or razor blade unit comprising at least one razor blade held on a blade support and having a surface adjacent the razor blade and sweeping over the user's skin during shaving, more particularly a cap, of plastics such as polystyrene or ABS or metal provided with means to increase slidability, characterised in that the means consists of a layer of a thickness of 5 to 1000 µm of a mixture, cured by UV irradiation, of water-soluble polymer, more particularly poly-N-vinylpyrrolidone or a copolymer thereof, one or more radically polymerisable vinyl monomers and a photoinitiator which decomposes into radicals on irradiation.

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