Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1997-04-09
1998-11-03
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521 81, 521146, 521148, C08J 908, C08J 914
Patent
active
058309241
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to monovinyl aromatic polymer foams. More particularly, this invention relates to non-linear monovinyl aromatic polymer-based foams.
Monovinyl aromatic-based resins, such as, for example, styrene-based resins, are well-known and widely employed in transformation processes into molded and/or extruded articles. In these processes, styrene-based resins having lower melt flow rate (such as from 0.5 g/10 minutes to 5 g/10 minutes) are usually preferred. The physical properties of such monovinyl aromatic polymers, also known as styrenic polymers, generally improve as the molecular weight increases. The processability of such monovinyl aromatic polymers, however, generally decreases as the molecular weight increases. Accordingly, the choice of a monovinyl aromatic polymer having sufficient properties usually involves a compromise between physical property requirements and processing requirements.
One approach to improve the processability of monovinyl aromatic polymers has been the addition of processing aids, such as plasticizers. It is known that the addition of plasticizers to polymer resins reduces the viscosity and increases the processability while decreasing the physical strength thereof. A problem frequently encountered with the use of such plasticizers is that they also reduce certain properties of such polymers.
Another approach has been the use of specific copolymerizable monomers in the polymerization process. Suitable copolymerizable monomers include polyfunctional monomers such di-, tri- or tetrafunctional monomers, such as, for example divinylbenzene, di(meth)acrylates, tri(meth)acrylates, and allylic compounds copolymerizable with the monovinyl aromatic monomer(s).
It also is common practice to improve the physical properties of styrenic polymers by modifying the styrenic polymer matrix with toughening agents such as rubbers. However, the addition of toughening agents is known to affect the processability of styrenic polymers adversely.
Japanese Patent Application 61-87713 describes a process of producing randomly branched styrenic polymers having molecular weights above 540,000 and improved physical properties, such as mechanical strength, as well as good processability. The styrenic polymers described contain a substantial level of residual toluene (approximately 6 percent). It is believed that this styrenic polymer has a high melt flow rate due to the presence of volatile components. Likewise, adverse effects on the Vicat heat distortion temperature and melt strength properties of this polymer would be expected. The process comprises the use of one or more organic peroxides, such as alkylperoxy-alkylfumarates.
Styrenic polymers are known to be useful in a large variety of applications. For example, thermoplastic foams such as styrene polymer foams which are widely used in the fields of construction, civil engineering and thermal insulation. The styrene polymer foam suitable for such applications desirably has relatively small cells and dimensional stability. These foams are the so-called extruded foams. Extruded foams are also employed in the so-called decorative field wherein a foam plank may be cut into a decorative foam and be used as is or used as a base for further decorative material.
Extruded foams and their manufacture are discussed in U.S. Pat. Nos. 2,409,910; 2,515,250; 2,669,751; 2,848,428; 2,928,130; 3,121,130; 3,121,911; 3,770,688; 3,815,674; 3,960,792; 3,966,381; 4,085,073; 4,146,563; 4,229,396; 4,312,910; 4,421,866; 4,438,224; 4,454,086 and 4,486,550. For a considerable period of time, styrene polymer foams have been extruded employing a variety of organic blowing agents, such as chlorofluorocarbons (CFC's), hydrochlorofluorocarbons (HCFC's), and other fully halogenated hydrocarbons as well as mixtures thereof. An alternative blowing agent system utilizing carbon dioxide and an alkane is set forth in U.S. Pat. Nos. 4,344,710 and 4,424,287.
Due to increased environmental concerns about ozone depletion, greenhouse effects and air quality in general, la
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Demirors Mehmet
Suh Kyung
Vo Chau V.
Foelak Morton
The Dow Chemical Company
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