Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
  • C08F283/006—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polymers provided for in C08G18/00

Definitions

• the present invention relates to new polymers comprising the reaction product of a polyurethane resin and acrylic monomers, the process by which the polymers are produced and applications of the polymer formed.
• Acrylic/polyurethane polymers and polymer compositions have been made by a number of techniques.
• One such method involves reacting 2-hydroxyethyl acrylate with an isocyanate terminated prepolymer to produce an acrylate-terminated polyurethane with pendant ethylenically
• Another method is to polymerise a mixture of polyols, isocyanates, acrylic monomers and peroxides ensuring simultaneous polymerisation of acrylic monomers to produce a polyacrylic polymer and of the polyols and isocyanates to form a polyurethane polymer in an
• interpenetrating network In these interpenetrating polymer networks the two polymer types remain as discrete molecules forming distinct but intertwining continuous polymeric domains, physically entangled but with no covalent bonds between polymer types.
• the present invention provides a single phase graft copolymer which comprises the free radical
• (meth) acrylic monomers refers to both acrylic monomers and methacrylic monomers.
• (meth)acrylates refers to acrylates and methacrylates.
• the (meth)acrylic monomers useful in the invention include those of formula (I) below:
• R 1 is hydrogen or methyl and R 2 is hydrogen or a C 1-20 branched or straight carbon chain which may be
• the polyurethane is the reaction product of an isocyanate monomer including at least one of the above features, for instance isophorone
• isocyanatomethylene groups and 4,4'-dicyclohexylmethane diisocyanate (which contains a methylene group bonded to two isocyanate groups via 1,4-cyclohexylidene groups).
• isophorone diisocyanate is particularly preferred
• the polymers of the present invention preferably comprise blocks of
• the polymers of the invention are copolymers of formula (II)
• R 1 and R 2 are as defined in relation to formula (I);
• U 1 and U 2 are blocks of polyurethane polymer optionally containing further graft points;
• A is a block of poly (meth)acrylic polymer.
• the carbon atom marked with an asterisk is a graft point, ie the carbon atom of the activated methylene group, preferably the methylene carbon atom in the
• the graft copolymer of the invention comprises at least 1% by weight and up to or more than 10% by weight of polyurethane based on the weight of the
• copolymer and may comprise up to 50% by weight of polyurethane based on the weight of the copolymer.
• the invention further provides a single phase graft copolymer obtainable by free-radical polymerisation of a (meth) acrylic monomer in the presence of a polyurethane and a solvent.
• polyurethane shows further advantages in the low temperature region; improvements may be seen in reduced cold cracking (after repeated heating and cooling cycles) and increased low temperature flexibility (see Test Example 2). Increased solvent resistance and improved adhesion are also obtained with polymers of the invention. This suits the polymers of the invention for use in coatings, especially vehicle refinishing coatings (paints, varnishes and primers), in which the polymer of the invention acts as binder and the other components are standard.
• the present invention further relates to a process for the preparation of a copolymer as defined above, which process comprises reacting a polyurethane with a
• (meth)acrylic monomer in the presence of a solvent or dispersion medium and free radical initiator.
• the process is preferably conducted at or about the boiling point of the mixture, for instance from 60 to 150°C, depending on the choice of solvents or dispersion medium and curatives.
• Any conventional free radical initiator is suitable for use in the polymerisation reaction, for example peroxide initiators such as benzoyl peroxide, lauryl
• Solvents which may be used include inert or active-hydrogen containing organic solvents, such as
• solvents include methyl ethyl ketone and toluene.
• the free-radical graft polymerisation reaction may be conducted using active-hydrogen containing solvents, such as alcohols, but only when the polyurethane resin has no, or only very few, remaining free isocyanate groups. If free isocyanate groups are present in the polyurethane, it is preferred to use a suitable insert solvent as described below.
• the free radical graft polymerisation may also be conducted in non-solvent dispersion media, such as aqueous media optionally containing surfactants or emulsifying agents. Again active hydrogen-containing media are preferably avoided when the polyurethane still contains a significant proportion of free isocyanate groups, for instance over about 2% free
• isocyanate groups are preferred.
• Water for instance demineralised water, and aqueous surfactants, such as sodium lauryl sulphate, are preferred.
• the initiator it has been found particularly convenient to use a mixture of methyl ethyl ketone and toluene, for instance at from 1:4 to 1:1, preferably 1:2 by volume.
• the polyurethane may be produced by reacting
• terminal isocyanate groups is formed and this prepolymer is then optionally further reacted with (c) a difunctional primary or secondary active hydrogen containing chain extender, such as an amine or alcohol, in the presence of a suitable solvent or diluent.
• a difunctional primary or secondary active hydrogen containing chain extender such as an amine or alcohol
• polyurethane are those which are inert to the isocyanate reagent, i.e. which do not contain active hydrogens; water, alcohols and amines are therefore to be avoided at this stage.
• Preferred solvents for this stage are organic solvents such as acetates, ketones and aromatic and
• Diluents which may be used in addition to or in place of solvent include liquid organic compounds such as
• (meth) acrylate monomers which are to be used in a subsequent stage of the reaction provided that these are inert to the reaction conditions during the polyurethane polymerisation, for instance when there is no free radical initiator present .
• the free radical graft polymerisation reaction will occur in the presence of low concentrations (for instance less than 10%, preferably less than 5% by weight) of free isocyanate groups so it is not essential that all isocyanate groups are consumed during production of the polyurethane. It is, however, preferred that the number of free isocyanate groups is kept to a minimum by use of appropriate
• the diisocyanate monomer (a) may be any aliphatic or aromatic diisocyanate but is preferably isophorone
• diisocyanate hexamethylene diisocyanate or 4,4'-dicyclohexylmethane diisocyanate; most preferably, the diisocyanate monomer is isophorone diisocyanate.
• the active hydrogen component (b) may be a diol, such as poly(tetramethylene glycol) or or preferably a
• polypropylene glycol a polyol such as a polyether polyol, polyester polyol or a polycaprolactone polyol.
• the chain extender (c) may be any difunctional primary or secondary amine or alcohol, for example isophorone diamine, ethylene diamine, 4,4'-diphenylmethane, or 4,4'-dicyclohexylmethane diamine or dimethylol propionic acid and is preferably isophorone diamine.
• the (meth) acrylate monomers may be those defined by formula (I) above, and are preferably methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-hydroxyethyl acrylate, acrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, propyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, lauryl methacrylate, stearyl methacrylate, 2-hydroxypropyl methacrylate, methacrylic acid, or a mixture of any two or more of the above mentioned monomers, and most preferably methyl methacrylate is used.
• the molecular weight (eg as determined by gel
• graft copolymer materials produced may range from 1,000 to 500,000 and is usually approximately 150,000 to 250,000.
• Fig. 1 shows a 400x magnification of a dried polymer film made using a polymer of the invention
• Fig. 2 shows a 400x magnification of a material, not of the invention, where mechanical blending has been used to mix a polyurethane and a polymethacrylate, and
• Fig. 3 and Fig. 4 show 1H n.m.r. fourier transform spectra of isophorone diisocyanate in d-chloroform and the reaction mixture at completion of the polymerisation
• Figure 1 clearly shows that the film formed of the polymer of the invention comprises a single phase copolymer whereas Figure 2 shows the separate phases which result from physically blending two polymer types.
• Isophorone diisocyanate (200.6g) was introduced to a vessel under nitrogen.
• Polycaprolactone diol (1000 MWt - 426g) and toluene (412g) were added and the reaction mixture was heated to from 80 to 85°C and held for 3 hours to reach a final isocyanate content of from 3.8 to 4.1%.
• reaction product was then cooled to from 25 to 30°C and toluene (56g), isopropanol (470g) and
• isophorone diamine (56g) were added with vigorous stirring.
• the resultant product had a Brookfield viscosity of from 15,000 to 25,000 mPa s at 25°C.
• Polyurethane prepared according to part (a) above (110g) and methyl ethyl ketone (260g) were introduced into a vessel fitted with a condenser and heated to a reflux temperature of from 80 to 85°C.
• Methyl methacrylate (315g) was added slowly with a simultaneous addition of benzoyl peroxide (4g).
• the mixture was reacted for 4 hours at reflux temperature, then toluene (378g) was added, followed by cooling.
• the resultant product had a Brookfield
• Isophorone diisocyanate (157g) was introduced to a vessel under nitrogen.
• Polycaprolactone diol 1000 MWt - 335g was added and the reaction heated to from 80 to 85°C and held for 3 hours to reach a final isocyanate content of from 6.2 to 6.4%.
• reaction mixture was then cooled to from 25 to 30°C and propyleneglycol monomethyl ether (1647g),
• Caromax 15/18 aromatic hydrocarbon (330g) and isophorone diamine (61g) added with vigorous stirring.
• Isophorone di-isocyanate 200 g
• a polypropylene glycol 800 G having a hydroxyl number of 28.05 mg
• demineralized water 506g
• sodium lauryl sulphate 50g of 30% aqeuou ⁇ solution.
• hydrazine monohydrate (3.75g) was added to the obtained dispersion. This mixture was allowed to react for half an hour whereafter further demineralized water (388.5g) was added and the whole dispersion heated to 85°C. The temperature of 85°C was maintained during the following addition. From two separate dropping funnels methyl
• methacrylate 112.3g
• potassium persulphate 2.5g in 100g of water
• the resulting graft copolymer was maintained at a temperature of 85°C for a further 1% hours. It was then cooled to less than 40oC.
• the resulting product shows GPC molecular weight distribution consistent with graft polymerisation, which is also supported by H 1 N.M.R. results for the relevant stages.
• Methyl methacrylate was polymerised using a peroxide initiator in the presence of isophorone
• the resultant material was analysed by n.m.r. Fourier Transform spectroscopy using a Jeol GX-270 MHz spectrometer and chloroform as solvent. Due to the low definition and high interference it was not possible to observe proton abstraction from the isophorone at position 1, which would have been expected on theoretical grounds. However, during the course of reaction, disappearance of the peak at d3.05 was observed. This was interpreted as showing abstraction of the secondary type isocyanatomethylene protons at position 7 and was not expected. In the reaction product this peak was replaced by a doublet at d2.96. The final n.m.r. spectrum is shown in Figure 4 and may be compared with that of isophorone diisocyanate in Figure 3.
• Methyl methacrylate was polymerised using a peroxide initiator in the presence of 1,6-hexamethylene diisocyanate. Again the n.m.r. results suggest the following

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polyurethanes Or Polyureas (AREA)

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• 1991
  • 1991-02-22 GB GB919103717A patent/GB9103717D0/en active Pending
• 1992
  • 1992-02-24 EP EP19920905372 patent/EP0572485A1/de not_active Withdrawn
  • 1992-02-24 WO PCT/GB1992/000328 patent/WO1992014768A1/en not_active Application Discontinuation

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