Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-04-18
2004-11-23
Sellers, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C264S331120
Reexamination Certificate
active
06822055
ABSTRACT:
The present invention relates to a method for producing a flat article comprising a material that contains polyreaction products. The method comprises the following steps: carrying out pre-crosslinking of a mixture comprising an epoxidation product of at least one carboxylic acid ester using at least one crosslinking agent to form a moldable material; molding the moldable material in the shape of a flat article; and curing the molded material to produce a flat article, wherein the pre-crosslinking reaction is separate from the curing reaction. The invention further relates to a moldable material that can be stored and to a flat article that can be obtained therefrom.
Linoleum has long been known as a resilient floor covering based on renewable raw materials. Because of its natural constituents, linoleum has achieved great importance based on its biological suitability for use in construction as well as environmental considerations. However, in the production of linoleum coverings the last step of the process requires a heat treatment, the so-called “ripening time,” that lasts several weeks. Although measures have been undertaken in the prior art to shorten this ripening time and thus achieve higher productivity, continuous methods for producing linoleum flooring are thus far unknown in the art.
For this reason flat articles, based on renewable raw materials, that are composed of other materials have been described in the prior art. German Patent 22 41 535, for example, describes a coating material for flat textile articles based on epoxidation products of esters of unsaturated fatty acids and polyvalent aliphatic alcohols.
However, the epoxidized oils and fatty acids used in such a method are liquid in the unprocessed state, with the result that flat articles cannot be molded from said substances in the raw state. Thus, in the production of flat articles from such a material it is common to carry out pre-crosslinking of the oils and/or fatty acids to give a highly viscous, moldable intermediate product (prepolymer). After molding into flat articles, a second crosslinking step is then carried out to give a usable material (final crosslinking). Termination of the first crosslinking step is problematic. In principle, a two-step reaction can be carried out in the following manner:
(I) Pre-crosslinking in which one of the crosslinking components is present in deficit (epoxidation product or crosslinking agent). Full crosslinking is carried out with addition of the component present in deficit.
(II) Different temperatures in the individual process steps.
(III) Use of separate crosslinking agents having different reactivities.
(IV) Different mechanisms in both process steps.
International Patent WO 90/107607 describes a method in “two reaction phases,” whereby in the first reaction phase a mixture of a stand oil with fillers is homogenized, then partially polymerized and partially crosslinked at elevated temperatures, using a peroxide, to give an intermediate product. The powdered intermediate product is then homogenized with an elastomeric natural or synthetic material, fillers, and a peroxide, and is again crosslinked and polymerized at elevated temperature.
Coating materials that are based on renewable raw materials and used for coating flat textile articles or release paper are known from German Patent Application 41 35 664. The coating materials are composed of a combination of epoxidation products of esters of unsaturated fatty acids and partial esters of polycarboxylic acids with polyether polyols in addition to a hydrophobing agent. These coating materials are used for the production of floor coverings. It is disadvantageous, however, that the top layer of coverings produced in this way is very rough and non-transparent. Furthermore, the surface of these coverings is not sufficiently soil-repellent and exhibits poor through-hardening.
Spreadable coating materials for the production of flat articles based on renewable raw materials are known from International Patent WO 96/15203. However, due to the use of so-called “coating pastes” contained in the coating materials, the production of said flat articles is limited to coating methods.
International Patent WO 98/28356 describes a method for producing flat articles based on renewable raw materials, in which flat articles with satisfactory material properties can be obtained by pressing, calendering, or extruding. An intermediate product that can be stored (prepolymer) is obtained, however, only if either the crosslinking agent or the epoxidation product is present in deficit. The prepolymer is converted to the fully crosslinked material in the second crosslinking step by addition of the component that is present in deficit. This method has the disadvantage that a considerable portion of the component first added in deficit must be compounded into the already viscous, pre-crosslinked material.
Since the reactions underlying pre-crosslinking and final crosslinking in the prior art are always based on the same reaction mechanism, it is difficult to obtain a further processable, storable intermediate product by timely termination of pre-crosslinking or by use of a component in deficit.
The object of the present invention, therefore, is to provide a novel method for producing a flat article from renewable raw materials in which essentially no ripening time is necessary and in which the rate of pre-crosslinking can be better regulated. A further object is that the pre-crosslinked intermediate product has a practically unlimited storage life.
This object is achieved by the embodiments characterized in the claims.
In particular, a method for producing a flat article comprising a
material that contains polyreaction products is provided which comprises the following steps:
(1) Compouding of an epoxidation product of at least one carboxylic acid ester using at least one crosslinking agent,
(2) Pre-crosslinking or partial crosslinking of the mixture obtained in step (1) to form a moldable material,
(3) Molding of the moldable material obtained in step (2) in the shape of a flat article, and
(4) Curing, further crosslinking, or final crosslinking of the molded material to produce the flat article,
wherein the pre-crosslinking reaction in step (2) is separate from the curing reaction in step (4).
The present invention is based on the knowledge that the disadvantages of known methods of the prior art can be avoided by having separate chemical reactions or chemical reaction mechanisms for pre-crosslinking and for curing. To this end, at least two different reactions I and II occur in the mixture obtained by compounding (1), for example by the presence of at least two crosslinkable groups A and B. For pre-crosslinking in step (2), essentially only one reaction I proceeds, for example by reaction of only one crosslinkable group A, that is, a class of similar crosslinkable groups. Reaction II, which is different from reaction I, does not proceed significantly under the reaction conditions for pre-crosslinking. For example, group B, which is different from A, is essentially stable or inert under the reaction conditions for pre-crosslinking, and in this step is practically unreacted. Reaction I, for example, halts after the consumption—that is, the essentially complete reaction—of group A to produce the moldable material. Furthermore, a suitable agent can be used to terminate reaction I after a desired reaction rate is achieved to produce the moldable material.
According to the invention, the second crosslinking step, that is, reaction II—the reaction of group B, for example—is initiated or started only by modification of the reaction conditions. In the context of the present invention, “modification of the reaction conditions” means an elevation in temperature or an increase or decrease in pressure, addition of reaction-initiating agents such as radical-forming initiators, and/or exposure of the mixture obtained in step (1) or the partially crosslinked material obtained by pre-crosslinking (2) to radiation, such as UV, electron beam, or IR radiati
Ess Miko
Fischer Bernd
Hamann Heiko
Kastl Bernd
Mauk Hans-Jörg
DLW Aktiengesellschaft
Sellers Robert
Womble Carlyle Sandridge & Rice PLLC
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