Foamed Articles

Foam sheet made of a biodegradable resin composition have been reported. The biodegradable resin composition contains a wax or a polyolefin resin. The biodegradable resin is mainly composed of PLA. Natural candelilla wax or paraffin wax is preferable as the wax. PE is preferable as the polyolefin resin. Also disclosed are a foam article and a molded container made of such a foam sheet wherein the degree of crystallinity of the biodegradable resin is 10% or more. 

For environmental reasons, foam articles have been developed that are made from biodegradable resins such as PLA, PBSU, PCL, poly(ethylene succinate), and poly(butylene terephthalate-co-adi-pate) (30). 

These materials can be degraded by moisture or microbes. Further, the materials and can be treated for composting in composters. Among these polymers, in particular, PLA has come into use in various applications as an ideal polymer that is a plant-derived raw material produced by polymerizing lactic acid obtained by fermenting materials such as various starches and sugars, and eventually 

However, compositions derived from PLA and aliphatic polyesters exhibit a high gas permeability. This is a drawback for packag-ing applications of food. 

The preparation of a foamed article includes the following steps (30)  

---

These methods rely on temperature changes, alternation of channel dimensions and flow rates, to produce foamed articles of a required structure, which is important for manufacturing foamed and foam-filled articles made of plastics, as well as for equipment design in this sphere. 

The surface finish of injection-moulded foamed articles are not ideal because of external defects, burst bubbles, etc. This can be avoided by sandwich moulding. This is accomplished by initially injecting a slug of polymer melt into the mould followed immediately by a polymer containing a blowing agent, which chases the initial polymer into all the interstices. 

The heat distortion temperature of styrene polymers is insufficient for some applications, but can be improved by copolymerization with monomers such as -methylstyrene or maleic anhydride. Maleic anhydride copolymers are excellently suited to the manufacture of foamed articles. The advantages of glass-fiber reinforcement are greater in such copolymers than in polystyrene itself. 

Polyethylene terephthalate) (PET) has become a major synthetic polymer during the past forty years. Significant commercial markets [1] have been developed for its application in textile and industrial fibers, films, and foamed articles, containers for carbonated beverages, water and other liquids, and thermoformed applications (e.g. dual ovenable containers). 

Patent Number US 6166096 A1 20001226 PRE-EXPANDED PARTICLES OF POLYPROPYLENE RESIN, PROCESS FOR PRODUCING THE SAME AND PROCESS FOR PRODUCING IN-MOULD FOAMED ARTICLES THEREFROM... 

Patent Number US 6110986 A1 20000829 PROPYLENE-BASED POLYMER COMPOSITION AND FOAMED ARTICLE THEREOF... 

Patent Number US 6083434 A1 20000704 ROTATIONAL MOLDING PROCESS FOR PRODUCING FOAMED ARTICLES... 

Control of polyethylene melt strength and melt viscosity has been used to produce foamed articles. 

Patent Number EP 928805 A2 19990714 PROCESS FOR MAKING FOAM ARTICLES FROM HIGH MELT STRENGTH PROPYLENE POLYMER MATERIALS... 

A material, such as (a) a terpolymer of propylene, ethylene and butene-1, (b) a polyolefin composition, which includes about 31 to 39% of a copolymer of propylene and ethylene and about 58 to 72% of a terpolymer of propylene, ethylene and butene-1 or (c) a polyolefin composition, which includes about 30 to 65% of a copolymer of propylene and butene-1 and about 35 to 70% of a copolymer of propylene and ethylene, is irradiated and extruded through a die in the presence of a physical expanding agent and a cell nucleating agent to produce a structure having a density, which is at least 10 times less than the initial density of the material. The foam articles exhibit improved flexibility and low temperature toughness compared to conventional propylene polymer materials. 

The PP is produced by melt-kneading PP, an isoprene monomer and a radical polymerisation initiator, which has a high melt viscosity and a high melt tensile strength and is difficult to cause drawdown. Foamed articles made therefrom have a low density, high closed cell content, good appearance and excellent heat resistance. 

Patent Number US 5783611 A 19980721 COMPOSITION AND PROCESS FOR ROTATIONAL MOULDING FOAMED ARTICLES Strebel J J... 

Patent Number US 5859076 A 19990112 OPEN CELL FOAMED ARTICLES INCLUDING SILANE-GRAFTED POLYOLEFIN RESINS... 

Describes open cell foamed articles including silane-grafted single-site initiated polyolefin resins. The olefin polymer resin can be a polyethylene, a copolymer of ethylene, a C3-C20 alpha-olefin, or a copolymer of ethylene, a C3-20 alpha-olefin and a C4-C20 diene. The open cell foamed articles have good cushioning properties and can be non-allergenic. 

Patent Number US 5605936 A 19970225 FOAMED ARTICLES COMPRISING HIGH MELT STRENGTH PROPYLENE POLYMER MATERIAL... 

Using the manufacture of PP battery cases as an example, the authors show how to produce thin-walled (2-5mm), foamed articles with good surface properties by means of low pressure injection moulding. Neopor 35 was used as the blowing agent. 5 refs. 

Azodicarbonamide, c.f., Figure 7.2 is a common chemical foaming agent. It is also addressed as azobisformamide. The thermal decomposition of azodicarbonamide results in the evolution of nitrogen, carbon monoxide, and ammonia, which are trapped in the polymer as bubbles to form a foamed article. 

The process of mould filling should not be considered as completely understood and controlled 98>, though some important features of gas-filled system flow were established by Fridman and co-workers 99 100) who have explained the formation of laminated structures in low-pressure moulding of foaming melts and found the correlation between moulding conditions and morphologic macro-structure and properties of foam articles. 

Smith PJ, Cross BJ (1996) Foamed articles of styrenic and acrylic polymers blend. US Patent 6,063,485... 

A special type of injection moulding is the manufacture of foamed articles. The foaming process takes place in the mould, so that mould filling requires considerably lower injection pressures and mould closing forces. Very large mouldings can be made in this way. 

Stuart, J.B. Skarke, S.C. Ogita, T. et al. Flame retardant polyolefin resin pre-expanded particles and in-mold foamed articles prepared therefrom, PCT US Patent 6,822,023 assigned to Kaneka Corporation, 2001. 

Molded Objects Immersed in Liquids. Molded, non-foamed articles, such as drinking cups from rubber-modified polystyrene, are immersed... 

The particular case of polymer-oligomeric compositions creates new technological possibilities such as the preparation of foamed articles directly at the place of utilization by foaming solutions or pastes at room temperature or sl tly elevated temperatures. It als) leads to a considerable reduction of enei consumption as cOTii ed to traditional processing methods (extrusion, casting and pressing). 

Further Development of Technology. Foamed Articles Instead of Foamed Materials... 

The chemistry of organic isocyanates has gained tremendous technical importance in recent years, since through certain isocyanate reactions a vast variety of plastics, coatings, elastomers, and especially foamed articles have become available. In spite of the relatively high reactivity of the isocyanate group, reactions involving isocyanates are carried out in almost all cases under the directive influence of catalysts. 

Bimodal PE s (LCB = 0.01- 3 > 7) was lightly crosslinked. The PE-1 was prepared in the hrst reactor, and PE-2 was prepared in the presence of 15 - 65 wt% of PE-1 in the second reactor. The reaction could be carried out in the slurry, solution, or gas phase. blends (p < 885 kg/m ) were used for wrre/cable coating, weather-stripping, seals, foamed articles with closed, open or mixed cells, containers, medical appliances, drapes and coverings, hbers, tapes, tubes, pipes and hoses, bellows, boots, gaiters, footwear, etc. Cree etal, 1998... 

Foamed article. [Data from Hori,T. Ueki,K., us Patent 5,162,380, Nov. 10,1992. 

PROC 12 Use of blowing agents in manufactnre of foamed articles, indnstrial settings... 

Poly (styrene-co-acrylonitrile). See Styrene/acrylonitrile copolymer Poly (styrene-co-allyl alcohol). See Styrene/allyl alcohol copolymer Poly (styrene-co-butadiene). See Styrene/butadiene polymer Poly (styrene-co-divinylbenzene). See Styrene/DVB copolymer Poly (styrene-co-maleic anhydride). See Styrene/MA copolymer Poly (styrene-co-methyl methacrylate). See Styrene/methyl methacrylate copolymer Poly (styrene-co-a-methylstyrene). See Styrene/a-methyl styrene resin Poly (styrene-divinylbenzene). See Styrene/DVB copolymer Polystyrene, expandable Synonyms EPS Expandable polystyrene Expanded polystyrene XPS Definition Amorphous PS beads contg. pentane as a blowing agent and coated with a lubricant the polymer is converted to foamed articles with a closed cell structure by applic. of steam Properties Beads (0.4-1.5 mm diam.)... 

---