Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-11-20
2002-12-24
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S401000, C524S442000
Reexamination Certificate
active
06498209
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to new plastisols with improved qualities, as well as to the use of advantageous (meth)acrylate resin masses for the production of these new plastisols.
Plastisols are generally found as a two-phase system having one component as a plastic (binding material) and the second as a suitable softening agent. As a matter of principle, a large variety of different plastics are usable as binding materials. However, from a technical point of view, only rather few plastics are actually utilized. By far, the most important class of polymers that is utilized for this purpose are derived from polyvinyl chloride (PVC). However, from the point of view of environment considerations, the utilization of PVC is undesirable. The danger of dioxin formation in the case of fire and the corresponding contamination of the surroundings militates against the utilization of PVC.
For this reason, attempts have been made to create plastisols based on poly(meth)acrylates. See for example, DE-PS 934 498, FR-A 2,291,248 and EP 0 774 483 A2. As used herein, the terminology (meth)acrylates includes both acrylates and methacrylates.
A fundamental problem associated with the use of poly(meth)acrylate plastisols in comparison to PVC plastisols rests in their insufficient shelf-life and mechanical properties. The use of spray-dried emulsion polymerisates based on PMMA in accordance with the state of the art, leads in combination with commercially available softening agents to good gelation and film properties, but also to reduced storage stability—the products already gel after comparatively short time at room temperature which can be recognized by an increase in viscosity.
The problem of storage capacity was attempted to be solved as disclosed in EP 0 774 483, by raising the amount of the middle sized particles by providing milled-suspension polymerisates to the usual emulsion polymerisates. The disadvantage of this procedure is in the circumstance that the higher particle size leads to impeded gelling of the plastisols, since under certain circumstances, the larger suspension polymerisates no longer gel completely which this technology demands. The inhomogeneity of the films caused by the incomplete gelation gives rise to insufficient mechanical properties with respect to tensile strength (resistance to tearing) in the corresponding films. Furthermore, one must not ignore the optical disadvantage of these inhomogeneous films in the formation of smooth surfaces. In order to achieve the production and reduction in size of the suspension polymerisates, additional procedural steps are required which lead to increase in cost of the product.
Furthermore, the art similarly requires the lowest possible viscosity level for the plastisol. On the one hand, it is desirable to cover the broadest possible spectrum of processing techniques and thus cover the widest possible area of usage. On the other hand, plastisols should desirably be processable at the lowest possible temperature and only after warming and subsequently cooling, should the plastisol gel to a solid uniform film.
The state of the art describes the use of emulsion polymerisates up to a molecular weight of 2,000,000 g/mol (EP 0 539 031 A1). For technically usual PMMA plastisols, there are utilized emulsion polymerisates of a substantially lower (less than 500,000 g/mol) molecular weight.
Heretofore, the state of the art does not describe polymerisates and/or copolymerisates of the utilized (meth)acrylate with such high chain lengths for the formation of plastisols. Thus, there is no suggestion to one skilled in the art that by utilizing polymerisates and/or copolymerisates of (meth)acrylates of such high molecular weight, one could obtain the above-described advantageous plastisols. On the contrary, one skilled in the art would be under the impression that by raising the molecular weight and therewith chain length polymers, there would be obtained an increase in the viscosity of the plastisols. In fact, as is shown in Table 1 hereof, what occurs is the exact reverse.
The task of the present invention is to find a plastisol that combines good film qualities and gel formability which lead to good tensile strength and break/extension properties of the product with acceptable storage stability and low viscosity. These and further named tasks, which will be clear to one skilled in the art from the state of the art, are solved by plastisol defined by claim 1 hereof.
SUMMARY OF THE INVENTION
Advantageous embodiments of the invention are set forth in claims relating back to claim 1. Uses of plastisols in accordance with the present invention are described in the corresponding claims.
These plastisols show:
1. Polymerisates and/or copolymerisates of (meth)acrylates obtainable by the polymerization of mixtures containing, as polymerizable components:
(A) 20 to 100 wt. % methylmethacrylate.
(B) 0 to 80 wt. % of (meth)acrylates different from methylmethacrylate, having formula I:
wherein
R
1
is hydrogen or methyl, and
R
2
is a linear or branched (C
1
-C
18
) alkyl residue.
(C) 0 to 40 wt. % of further monomers different from (A) and (B),
(D) 0 to 40 wt. % of adhesion causing monomer, wherein (A) through (D) yield 100 wt. % of the polymerizable components.
II. A compatible softening agent in the proportion of 5 to 400 parts by weight, relative to 100 wt. % of polymerisate and/or copolymerisate I.
III. Inorganic fillers in the amount of 9 to 700 parts by weight, relative to 100 parts by weight of component I, characterized thereby that the mean molecular weight M
w
of the poly-merisate and/or copolymerisate of the (meth)acrylate is greater than 3,500,000 g/mol, enables one to provide, a particularly advantageous and yet surprisingly stable plastisol having low viscosity which, because of homogeneous film formation on gelation, show excellent mechanical as well as optical properties. The polymerisate and/or copolymerisates are preferably obtained through emulsion polymerization.
Under normal circumstances, a rise in molecular weight, that is to say chain length, in solutions or emulsions of polymer, leads to a faster separation of mixtures and thus a poorer storage life. However, contrary to expectations, the storage stability of plastisols improves with the increase in chain length. In the plastisols of the present invention, one observes a far lower level of mixture separation than with plastisols formed with polymerisates of the state of the art.
Especially preferred in the plastisols of the present invention based on (meth)acrylate, are those wherein the residue R
2
of the (meth)acrylate of formula I is a linear or branch chained (C
1
-C
8
) alkyl residue.
It is particularly advantageous if the mean molecular weight M
w
of polymerisate and/or copolymerisate of the charged (meth)acrylate in the plastisols is greater than 3,500,000 g/mol., suitably greater than 3,900,000 g/mol.
DISCUSSION OF THE PREFERRED EMBODIMENTS
Particularly desirable for the formation of plastisols is the use of polymerisate and/or copolymerisate of the (meth)acrylate with a mean molecular weight M
w
of greater than 3,500,000 g/mol, preferably greater than 3,900,000 g/mol.
The term “(meth)acrylate” within the scope of the present invention includes both acrylates and methacrylates.
The chain length of the polymerisates and/or copolymerisates of the methacrylates are limited by a synthetically achievable chain lengths. Chain lengths having a mean molecular weight of M
w
of about 12,000,000 g/mol are achievable.
The mean molecular weight M
w
of polymers for use of the present invention are determined by means of SEC or GPC (size exclusion chromatography or gel permeation chromatography) relative to polystyrene standards. Those skilled in the art are familiar with SEC or GPC analysis methods for the determination of the mean molecular weight.
Within the scope of the invention, a further quantity for the characterization of the molecular mass of the charge polymerisate and/or copolymerisate is the viscosity number VZ. This viscosity numb
Belik Pavel
Dorn Klaus
Loehden Gerd
Schickel Natascha
Schneider Georg
Niland Patrick D.
Roehm GmbH & Co. KG
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