Process for preparing one-component type sealant

Abstract: There is disclosed a process for preparing a one-component type sealant, comprising the steps of mixing powdery raw material such as prepolymer and additives admixed or not admixed with a predetermined amount of plasticizer in a mixer in a hermetically closed system, continuously degassing the mixed pasty material in a degassing line, and mixing the degassed mixture with catalyst admixed or not admixed with plasticizer.

Description: The present invention relates to a process for preparing a one-component type sealant, and more specifically to a process for preparing a one-component type sealant, which can be continuously and efficiently prepared without being affected by the environmental conditions of the manufacturing site while maintaining the level of properties of a product within a given range. From the document "Kunststoff-Maschinen-Fuhrer", F. Johannaber und K. Stoeckhert, Carl Hanser Verlag, 1984, there are known mixing machines for the production or processing of plastics wherein it may derived from the machines disclosed in said document that the latter are suited to carry out a process for preparing mixtures of powders and additives including the step of mixing the same. Moreover, said document also refers to machines for operation under vacuum which might result in degassing of corresponding mixtures. EP-A-119 696 discloses a method for producing a low density foamed polyester resin, wherein said resin is metered from a storage zone, heated in a heating zone, forwarded to a first mixing zone where a minor amount of a blowing agent is added and mixed with said polyester resin and further the activated resin is forwarded to a second mixing zone wherein it is mixed with a minor amount of a catalyst. GB-B-1,111,693 discloses a method and apparatus for making an expandable homogenous mixture, in particular phenol resin, wherein liquids are to be mixed under temperature control and wherein a third component is injected into a mixer. BE-B-640 357 discloses a method of preparing a mixture of polyvinyl powder in a liquid to form a homogenous suspension such as to obtain rapid fusion of the respective components upon heating. A method of mixing a first synthetic resin material, to be molded, with a plasticizer, and then mixing the resultant mixture with a second synthetic resin material to be molded, is known from JP-A-57-22009. A process for preparing a moisture-curing one-component type sealant has heretofore been known as a process for preparing a one-component type sealant. This process comprises mixing a preliminarily dried powder (e.g., carbon black, calcium carbonate, or the like) with prepolymer, and mixing catalyst with the resulting mixture. Since mixing is conducted with one mixer in the air, however, the process involves the following problems: (a) the productivity is very poor, and the quality of the product is liable to be unstable due to moisture in the air, (b) the dispersion between batches is large and the loss in the preparation is large, and (c) much labor and long time are needed for cleaning the equipment. The present invention has been made while paying attention to the above-mentioned problems of the conventional process. A first object of the invention is to provide a process for preparing a one-component type sealant which can be efficiently prepared without being affected by the environmental conditions of the manufacturing site by enabling a continuous preparation in a hermetically closed production line. A second object of the present invention is to provide a process for preparing a one-component type sealant, which can minimize the dispersion of properties such as the storage stability and the viscosity and enables the equipment to be cleaned only in specified parts thereof at a given interval of period. According to the present invention, the afore mentioned objects are achieved by a process comprising the steps of any of the appended claims 1 and 2, respectively. The attached figure is a block diagram of the process for preparing a one-component type sealant according to the present invention. An example of the present invention will now be described with reference to the figure. The figure shows a block diagram of the process for preparing a one-component type sealant according to the present invention. The process for preparing a one-component type sealant mainly involves a raw powdery material (e.g., carbon black or calcium carbonate as a reinforcing agent or an extender) feeding line 10, a prepolymer feeding line 20, a plasticizer feeding line 30, and a catalyst feeding line 40. Hermetically closed lines shielded from the outer atmosphere (an area surrounded by the dot-dash line) are constituted between storage tanks for the respective raw materials through filling machines. The constitutions of respective lines will now be described. The raw powdery material feeding line 10 leads to a powder storage tank 10C through a powder drier 10A and a powder cooler 10B. The raw powdery material discharged from the powder storage tank 10C is fed through a screw feeder 10F and a powder feeder 10E to a mixer 50 after weighing a given amount of the material. The procedure up to the storage of the above-mentioned powdery raw material in a storage tank 10C is as follows. The powdery raw material is preliminarily placed in a powder dryer 10A, wherein it is dried by steam heating and hot air supply while mixing it by stirring. It is then sent to a powder cooler 10B, wherein it is cooled with cooling water. The dried and cooled powder is stored in the powder storage tank 10C. In a prepolymer feeding line 20, a given amount of prepolymer is stored in a prepolymer storage tank 20A, and fed through a pump 20B, a flowmeter 20C, and a static mixer 20D to a mixer 50 which is used for mixing both the powdery raw material and the prepolymer. In a plasticizer feeding line 30, plasticizer (e.g., dialkyl phthalate or the like) is heated with steam, dehydrated by stirring under reduced pressure, and cooled in a dehydration tank 30A. It is then sent to a storage tank 30B, wherein it is stored. The stored plasticizer is then metered into preparation tanks 30E and 30F by using a pump 30C and a flowmeter 30D. A predetermined amount of additives is fed to the above-mentioned preparation tank 30E, wherein stirring is conducted under reduced pressure. Then, the resulting mixture is sent to a storage tank 30H, wherein it is stored. A predetermined amount of catalyst (e.g., comprising an amine or the like) is fed to the preparation tank 30F, wherein stirring is conducted under reduced pressure. Then, the resulting mixture is sent to a storage tank 30I, wherein it is stored. The above-mentioned plasticizer, additives and catalyst are kept at a constant temperature in storage tanks 30B, 30H, and 30I by circulation of temperature-controlling warm water. The reasons why minute amounts of the additives and the catalyst are added to the plasticizer to prepare master batches before they are fed to mixers 50 and 70 as described above are that uniform mixing and dispersion of the additives and the catalyst in mixers 50 and 70 are made possible thereby and that the metering accuracy is improved. Where a plurality of preparation tanks 30F and storage tanks 30I are provided, a plurality of sealants having different properties can be prepared while commonly using main equipments. The case where the above-mentioned raw materials are continuously mixed in a hermetically closed apparatus will now be described. The materials stored in the prepolymer storage tank 20A and the additives storage tank 30H are sent to a static mixer 20D under pressure while metering them with the pump 20B and the flowmeter 20C, and the pump 30K and flowmeter 30L, respectively. The materials are mixed together in the static mixer 20D and fed to a mixer 50. Simultaneously, the powder stored in the powder storage tank 10C is fed in a predetermined amount through a screw feeder 10F and a powder feeder 10E to a mixer 50, wherein it is mixed with the materials fed from the static mixer. If the temperature rises during mixing due to the presence of minute amount of water remaining in the raw powdery material, the reaction of prepolymer is promoted. Thus, mixing is conducted while cooling in a manner such that homogeneous pasty material can be obtained as fast as possible. The mixed pasty material is sent under pressure through a pump 50A into a degassing apparatus 60, wherein the pasty material is degassed under reduced pressure. In this degassing apparatus 60, the pasty material is degassed under reduced pressure at about 40° C. Thus, air contained in the pasty material is efficiently removed. By heating the pasty material, the load and pressure loss in starting due to the lowering in the temperature of the material during stoppage is decreased, and the extent of degassing is improved. The sealant which is prepared in a state of air being incorporated thereinto is not preferred from the viewpoint of properties required of the product and stability of the quality thereof. The material thus degassed is metered through a pump 60A and a flowmeter 60B into a mixer 70 and then a static mixer 80. The catalyst stored in the storage tank 30I is metered through a pump 40A and a flowmeter 40B into the mixer 70 and then the static mixer 80, wherein the catalyst is mixed with and dispersed into the paste. If the catalyst is fed to the system in the first step, there arises a fear that the prepolymer is hardened under the pressure of moisture in the air in any apparatus and peeled pieces of a hardened product is incorporated into the materials, because the hardening reaction is expedited from the time when it is fed to the system. In view of this, the catalyst is fed to the last mixer to be mixed with the pasty material which is in the most stable state because it is free from air by degassing. The mixed material is filled in a drum with a filling machine 80A or 80B. It is preferred that the plasticizer and the catalyst be mixed in amounts of 10 to 50% and 0.01 to 1%, respectively, based on 100% of the powder and the prepolymer. When the amount of the plasticizer is less than 10%, the hardness is so high that the resulting product is unsuitable as the sealant. When it exceeds 50%, the hardness is too low. Thus, the amount of the plasticizer is preferably in the range of 10 to 50%. When the amount of the catalyst is less than 0.01%, the reaction in practical use is slow. When it exceeds 1%, the pot life is short and the storage stability is deteriorated. Thus, such an amount is not preferred from the viewpoint of work and quality. Therefore, the catalyst is used preferably in an amount of 0.01 to 1%. According to the present invention, a one-component type sealant is prepared by continuous metering, mixing and degassing of the materials in hermetically closed equipments as described above, therefore the following excellent results are brought about. (a) The sealant can be prepared irrespective of environmental conditions of the manufacturing site. The dispersion of properties such as storage stability and viscosity can be remarkably decreased. (b) No loss due to adhesion of materials to a mixer is caused. (c) Cleaning of equipment which is necessary in every batch in the case of the conventional process becomes unnecessary, leading to improved workability. (d) The safety and productivity are improved by automatic operations.

Claims: Process for preparing a mixture of dry powder with additives including mixing and degassing said mixture wherein, in order to prepare a moisture curable one-component type sealant, said entire process is performed in a hermetically closed system, and in that it comprises the steps of: continuously feeding a dry powder material, a dry prepolymer and a dry plasticizer to respective storage tanks in said hermetically closed system; continuously feeding a predetermined amount of the powder material, a predetermined amount of the prepolymer, based on the amount of the powder material, a predetermined amount of the plasticizer, based on the amount of powder material and prepolymer, from said storage tanks, to a mixing and degassing zone; continuously mixing and degassing the mixture of powder material, prepolymer and plasticizer within said mixing and degassing zone; continuously adding with mixing to the degassed mixture a predetermined amount, based on the amount of the powder material, the prepolymer and the plasticizer, of a catalyst; and continuously discharging the resulting mixture to a filling means. Process for preparing a mixture of dry powder with additives including mixing and degassing said mixture wherein, in order to prepare a moisture curable one-component type sealant, the entire process is performed in a hermetically closed system, and that it comprises the steps of: continuously feeding a predetermined amount of dry powder material, a predetermined amount, based on the amount of the powder material, of a dry prepolymer, and a predetermined amount, based on the amount of the powder material and the prepolymer, of a first portion of a dry plasticizer, to a first mixer in said hermetically closed system to form a pasty mixture; continuously degassing the pasty mixture in the first mixer under reduced pressure; continuously passing the degassed pasty mixture to a second mixer; mixing separately a predetermined amount of catalyst, based on the amount of powder material, the prepolymer and the first portion of the plasticizer, with a predetermined amount, based on the amount of the powder material, the prepolymer and the first portion of the plasticizer, of a second portion of plasticizer, continuously feeding the mixture thus obtained to the second mixer; mixing the mixture of catalyst and plasticizer with the degassed pasty mixture in the second mixer; and discharging the resultant mixture in the second mixer to a filling means. Process for preparing a mixture of dry powder with additives according to claim 1, characterized in that, before mixing said catalyst with said degassed pasty mixture, it is mixed with a part of said plasticizer. Process for preparing a mixture of dry powder with additives according to any of claims 1 to 3, characterized in that minute amounts of additives are added to the plasticizer before mixing the latter with the powdery raw material and the prepolymer. Process for preparing a mixture of dry powder with additives according to any of claims 1 to 4, characterized in that master batches of plasticizer mixed with additives or catalyst are stored within said hermetically closed system. Process for preparing a mixture of dry powder with additives according to any of claims 1 to 5, characterized in that the amount of plastisizer falls within the range of 10 % - 50 %, based on the amount of the powder and prepolymer. Process for preparing a mixture of dry powder with additives according to any of claims 1 to 6, characterized in that the amount of catalyst falls within a range of 0,01 % - 1 %, based on the amount of powder and prepolymer.

Inventors: DANJO MASAMICHI, KABASAWA TAKAYUKI, KANO KOICHI, OKADA ETUO, DANJO, MASAMICHI, KABASAWA, TAKAYUKI, KANO, KOICHI, OKADA, ETUO
Applicants: YOKOHAMA RUBBER CO LTD, THE YOKOHAMA RUBBER CO., LTD.
Application year: 1987
Main classification: B29B7
IPC codes: C09K3, B29B7