Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-09-03
2001-01-30
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C525S084000, C525S085000, C525S086000, C525S902000
Reexamination Certificate
active
06180693
ABSTRACT:
The present invention relates to novel core/shell particles comprising an elastomeric core and a crosslinked polymer shell grafted thereto, to epoxy resin compositions comprising the novel core/shell particles, and to coatings and moulded materials produced from the epoxy resin compositions by curing. It is known, for example from EP-A-0 578 613, that addition of core/shell particles whose core comprises a rubber like material to curable epoxy resin compositions can significantly improve the mechanical properties, in particular the flexural and impact strength, of cured epoxy resins. These core/shell particles basically comprise a crosslinked insoluble core to which an uncrosslinked or slightly crosslinked shell is grafted by methods known in polymer chemistry. The shell comprising the graft polymer has a higher glass transition temperature than the core. Typically, the glass transition temperature of the core is <0° C. and that of the shell is >25° C. After the epoxy resin has been cured by means of conventional curing agents, these core/shell particles are in the form of a separate, discontinuous phase in the resin. An important property of the graft polymers forming the shell is their compatibility with the epoxy resin, which is effected, for example, by swellability of the shell in the epoxy resin. Whereas, on the one hand, the swellability of the shell in the epoxy resin makes an essential contribution to good compatibility with the resin, it is, on the other hand, the principal factor responsible for an undesired increase in the viscosity of the curable epoxy resin mixture, which considerably restricts the applicability of such epoxy resin compositions.
PCT Application WO 87/00188 expresses certain reservations regarding an excessive increase in the viscosity on use of core/shell particles having a high-molecular-weight shell as modifiers for epoxy resins.
J. Y. Qian et al. in “The Preparation and Application of Core-Shell Latex Particles as Toughening Agents for Epoxies”, 25th International SAMPE Conference, Oct. 26-28, 1993, describe the use of specific core/shell polymers for improving the fracture toughness in epoxy resins. Use is made, inter alia, of a core/shell polymer whose shell is crosslinked and, based on all comonomers, comprises 5% by weight of copolymerized divinylbenzene.
Compared with the other core/shell copolymers used, whose shell is not crosslinked, no improvement of the fracture toughness in epoxy resins is achieved.
J. Y. Qian et al. in Journal of Applied Polymer Science, Vol. 58, pages 439-448 (1995), confirm the above comments regarding the use of core/shell polymers comprising 5% by weight of copolymerized divinylbenzene in the shell. It is even noted therein that a crosslinked shell adversely affects the fracture toughness.
In JP Application Hei 4-297220, transparent thermoplastics are added to core/shell polymers comprising up to 5% by weight of a crosslinking component in the shell in order to improve the impact strength and retain the transparency.
Surprisingly, it has now been found that use of certain core/shell particles which have a shell comprising a relatively highly crosslinked polymer, in particular use of epoxy resins, gives processing advantages, since the novel core/shell copolymers do not significantly increase the viscosity of the liquid or molten epoxy resins. Epoxy resin compositions modified in this way allow simpler application conditions and a broader range of potential applications.
The present invention thus relates to novel core/shell particles comprising a core comprising an elastomer having a T
G
value of <0° C. onto which a shell of a crosslinked copolymer is grafted, where the proportion of the crosslinking component in the copolymer of the shell is from 5 to 90% by weight, based on the total amount of comonomers in the shell copolymer.
The core of the novel core/shell particles, which comprises an elastomer, can comprise, for example, a polybutadiene, polybutadiene derivative, polyisoprene, polychloroisoprene, silicone rubber, polysulfide, poly(meth)acrylate or a copolymer or terpolymer thereof with styrene or acrylonitrile. Such elastomers are known and are also commercially available, for example a polybutadiene latex under the name Baystal® S polybutadiene (Bayer AG). The core of the novel core/shell particles preferably comprises a crosslinked elastomer, for example polybutadiene, poly(meth)acrylate or a copolymer or terpolymer thereof with styrene, having a T
G
value of <−10° C.
In particular, the core of the novel core/shell particles comprises a polybutadiene or poly(meth)acrylate.
In the novel core/shell particles, the amount of the core, based on the total core/shell particles, is generally 10-90% by weight, preferably 20-80% by weight, in particular 30-70% by weight
The shell of the novel core/shell particles comprises a crosslinked copolymer based on vinyl monomers, which can contain functional groups, for example glyddyl, hydroxyalkyl, amino or amido groups, and based on polyfunctional (meth)acrylates of aliphatic polyols, bisphenol diglycidyl ether di(meth)acrylates, di(meth)acrylates of ethoxylated bisphenols, products of the addition reaction of (meth)acrylic acid with di- or polyepoxide compounds other than bisphenol diglycidyl ethers, or based on allyl (meth)acrylate or divinylbenzene as crosslinking component and comonomer. It is also possible to use mixtures of the various vinyl monomers and the crosslinking components.
Examples of suitable vinyl monomers are acrylic acid, methacrylic acid and derivatives thereof, for example (meth)acrylates, (meth)acrylates containing epoxide groups, for example glycidyl (meth)acrylate, (meth)acrylates containing hydroxyl groups, for example hydroxyethyl- or hydroxypropyl(meth)acrylates, or polyethylene glycol- or polypropylene glycol-derived (meth)acrylates of the formula I
in which either R
2
or R
3
is the
radical and the other radical is -H or an
alkyl, R
1
and R
4
are each -H or -CH
3
, and n is a number from 2 to 30, monomers containing amido groups, for example (meth)acrylamides, monomers containing amino groups, for example dimethylaminoethyl (meth)acrylate, or vinylpyridine, styrene, vinyl ether or acrylonitrile.
The vinyl monomers are preferably (meth)acrylic acid, (meth)acrylates, polyethylene glycol- or polypropylene glycol-derived (meth)acrylates of the formula I, styrene, acrylonitrile or glycidyl (meth)acrylate.
In particular, the vinyl monomers used for the preparation of the shell are at least one polyethylene glycol- or polypropylene glycol-derved (meth)acrylate of the formula I.
Suitable crosslinking components, i.e. monomers containing at least two vinyl groups in the molecule, are also mixtures of at least two vinyl monomers which can react with one another via a functional group during preparation of the shell, for example mixtures of (meth)acrylic acid and glycidyl methacrylate.
The crosslinking component used for the preparation of the shell of the novel core/shell particles is preferably a di(meth)acrylate of ethylene glycol, propylene glycol, butylene glycol or a higher homologue thereof having up to 30 recurring structural units of the formula
in the molecule, in which R
1
is -H, -CH
3
or -C
2
H
5
, furthermore
1,1,1-trimethylolpropane tri(meth)acrylate, bisphenol A-diglycidyl ether di(meth)acrylate or allyl methacrylate.
In particular, the crosslinking component employed in the preparation of the shell is ethylene glycol di(meth)acrylate or a higher homologue thereof.
In the novel core/shell particles, the amount of the shell, based on the core/shell particles, is generally 90-10% by weight, preferably 80-20% by weight, in particular 70-30% by weight.
In the shell itself, the proportion of the crosslinking component is preferably 6-40% by weight, in particular 10-50% by weight, based on the total amount of comonomers in the shell polymer.
The novel core/shell particles are prepared by methods known per se. Preference is given to a preparation as emulsion polymer in an aqueous medium. In this case, the core is
Behm Dean Tallak
Eldin Sameer Hosam
Mayer Carl Walter
Petschel Klaus
Roth Martin
Aylward D.
Dawson Robert
Kovaleski Michele A.
Vantico Inc.
LandOfFree
Core/shell particles, and curable epoxy resin composition... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Core/shell particles, and curable epoxy resin composition..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Core/shell particles, and curable epoxy resin composition... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2500823