Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2002-01-09
2004-04-06
Le, H. Thi (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S407000
Reexamination Certificate
active
06716527
ABSTRACT:
This invention relates to a pressure-sensitive hotmelt adhesive in the form of granules having at least one outer layer of at least one non-pressure-sensitive adhesive component of the pressure-sensitive hotmelt adhesive and a core of the other components of the pressure-sensitive hotmelt adhesive surrounded by said outer layer.
Coated granules such as these of pressure-sensitive adhesives to be applied from the melt are known. Thus, EP 531 927 describes a dimensionally stable pressure-sensitive hotmelt adhesive containing resins, elastomers and plasticizers as principal constituents. It is in the form of pellets or granules of which the surface consists of adhering powder of a meltable elastomer suited to the formulation. The powder-form elastomer preferably compensates for a small amount of the elastomer in the hotmelt adhesive of the core. The powdered granules are produced by depositing drops of the molten hotmelt adhesive onto a powder-covered conveyor belt and thus covering them with powder. The disadvantage of this is that the powder only affords the surface partial protection against unwanted sticking. This is because the granules show a tendency towards cold flow in the event of prolonged storage and block in the process, i.e. no longer flow freely.
Similar disadvantages arise with the free-flowing granules according to DE 20 34 038. These particles with a diameter of preferably 1 to 30 mm consist of an adhesive, dimensionally stable material in the core and a layer of powder on its surface. The particles preferably consist of an adhesive thermoplastic, more particularly an atactic polyolefin such as, for example, polybutene-1 or PP, and are covered with a powder layer of a special or similar kind of a hard thermoplastic, for example an isotactic polyolefin, such as polybutene-1. For their production, the particles to be powdered are formed by extrusion and cutting and are powdered in a fluidized bed simultaneously with the cooling of the particles obtained from the hot melt. The powder is solid. The particles to be powdered may be in an almost still liquid state or may be cooled to such an extent that they are only just tacky.
U.S. Pat. No. 4,359,492 describes the coating of pellets of tacky elastomeric materials with powder-form materials. The elastomeric materials are preferably pressure-sensitive adhesives while the powder-form materials are crumb-form polymers with a softening temperature of at least 95° C.
EP 294 141 describes coated pellets of synthetic polymers, for example EVA coated with PE. They are produced by
a) extruding a first synthetic polymer to form a strand or pellets,
b) cutting the strand while it is still molten into pellets,
c) powdering the pellets with powder of a second polymer, the powder melting under the effect of the high temperature of the pellets and forming a layer,
d) cooling the coated pellets.
The powder may be heated to 30-40° C. before application. The coated pellets do not stick to one another. The disadvantage of the described coated pellets is that the surrounding layer is not continuous, allowing parts of the melt to leak out (“bleeding”).
WO 96100747 describes a process for coating hotmelt adhesives which essentially comprises the following steps:
a) extruding the hotmelt adhesive through a suitable nozzle,
b) spraying the surface of the extruded hotmelt adhesive with a molten film-forming polymeric material of relatively low molecular weight or with a polymer formulation, the coating material having no significant effect on the properties of the adhesive composition after it has been remelted,
c) heating the surface of the coated adhesive so that the film-forming polymer is remelted and forms a continuous coating and
d) cooling the adhesive thus coated to temperatures suitable for handling.
The extruded hotmelt adhesive can be cooled after its extrusion and before its spray coating. However, it is preferably coated directly after extrusion. Finally, the coated extrudate is cut up. The disadvantage of this process and the resulting products is that the cut faces are not coated. Accordingly, the portions are not free-flowing.
EP 14 467 describes a process for the underwater granulation of ethylene copolymers, for example ethylene/vinyl acetate copolymers, in which 1 to 1,000 ppm of a surfactant are said to be added to the water to reduce agglomeration. The agglomeration temperature is thus increased by at least 10° C.
WO 97119582 describes a thermoplastic polymer composition with a non-tacky surface in the form of pellets of which 97 to 99.9% by weight consists of a pressure-sensitive adhesive and 0.1 to 3% by weight of a pelleting material which surrounds the thermoplastic composition. Materials from the group consisting of PE wax, modified PE wax, PA wax and stearamide wax and mixtures thereof are specifically mentioned as pelleting materials. They are in powder form. The document in question also mentions underwater granulation as a process for producing the tacky hotmelt adhesive pellets from which pellets with non-tacky surfaces which do not block are produced using the pelleting material. Production comprises the following steps:
producing a melt mixture from the starting components,
forming pellets with the aid of nozzles,
solidifying the pellets by cooling,
applying the pelleting material at certain places during the pelleting process and
drying.
The pelleting material is said to be applied during each extruder pass. It is added to the cooling medium. Its concentration in the water is between 0.1 and 3% by weight.
The disclosed process does not lead to the described products. More particularly, it does not lead to free-flowing granules after storage for 3 months at 30° C. for a layer thickness of the granules of 15 to 30 cm. The granules stick to one another and to the pack.
EP 156 274 describes a water-based release agent for the temporary antiadhesive surface finishing of tacky pellets, granules etc. which consists of a 0.5 to 25% by weight solution or dispersion of an at least difunctional aliphatic alcohol containing 3 to 7 carbon atoms and/or an at least trifunctional aliphatic hydroxycarboxylic acid or water-soluble salts thereof. 0.2 to 15% by weight of water-insoluble salts of a C
12−36
aliphatic or alicyclic mono- or dicarboxylic acid may be additionally used. The release agent is intended above all for the antiadhesive finishing of granules of hotmelt adhesives. To this end, the granules are treated with the solution or suspension at 18 to 22° C. and, after the solution or suspension has been removed under suction, the granules are dried for 15 minutes with warm air having a temperature of 30° C. The granules then contain 0.3 to 0.5% by weight of active substance. They can be protected. The release effect remains in tact for at least 3 months at 25° C. However, it is not sufficient for the storage temperature and the storage pressure to be increased. In addition, the finishing process is difficult on account of the agglomeration of the as yet non-finished granules.
German utility model 9116662.4 describes a packed adhesive composition where a quantity of substantially homogeneous separate portions of the adhesive composition is completely surrounded by a net or a bag of a plastic packaging material, preferably by a welded bag. The separate portions are preferably externally coated with a separating antiadhesive substance. Despite this antiadhesive substance, the portions stick to one another because of cracks in or flaking of the coating material, particularly after prolonged storage at varying temperatures. The surfaces of the individual adhesive portions are thus exposed and adhere to one another. This makes the hotmelt adhesives difficult to handle and, above all, to dose. To avoid this disadvantage, the adhesive portions—depite their antiadhesive coating—are packed in a bag which is then handled. The bag preferably contains 100 to 4,000 individual portions. The disadvantage of welding inadequately coated portions in a bag is that the entrapped air prevents the bag from being immersed in melting t
Czmok Michael
Hatfield Stephen
Kik Michael
Petry Gerald
Vogel Rainer
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Le H. Thi
LandOfFree
Hot-melt-type adhesive in the form of a granulate does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hot-melt-type adhesive in the form of a granulate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hot-melt-type adhesive in the form of a granulate will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3195680