JPS60500906A - Pressure molding method using salt core and composition for producing core - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Pressure molding method using salt core and composition for producing core field of invention The present invention relates to a pressure molding process, particularly the formation of a salt core or inert material and a relatively low melting temperature salt. Regarding molding methods that utilize molding cores made of mixtures of particles, ``The child melts the core from a product that has the core intact within it into a molten bath of core material. removed from the finished product.

Prior art and background of the invention No. 3, issued November 18, 1972, to W. R. Weaver. 69’2. , No. 551 (which is included here as a reference), describes the mixing of molten salt and sand. Pressure molding using a non-extrudable molding core manufactured by casting a compound The method is disclosed. Relatively low single point salt mixing as disclosed in this patent The use of extremely smooth porcelain-like surfaces is highly desirable in pressure forming processes. Manufacture cores with specific characteristics. Moreover, the use of sand as part of the core composition It has high compressive strength, which is a requirement for die castings and molded products made from plastic. A core is produced.

According to this patent, the core is either dip coated or surface coated with a molten salt bath on a solid sand core. Alternatively, sand may be mixed into a molten salt bath and the resulting liquid mixture may then be cast into core form. Therefore, it is manufactured.

This patent discloses that the core is dissolved as a solute in water or a weak acid solution. shing) and removal of the core from the finished product by leaching or mechanical vibration. is disclosed.

Summary of the invention In one aspect, the invention is based on the method disclosed in U.S. Pat. No. 3,962,551. The present invention relates to improvements in the process, particularly in the removal of salt cores from finished molded products. Book In the invention, on the one hand, the components are identical or substantially identical to the components of the core itself; melting of the components of the bath or placing the product on or in the molten salt bath. The core is removed from the product by melting it. Quite surprisingly, the melting temperature Removal of the core at high temperatures is easily accomplished and without adversely affecting the molded product. It will be done. The immersion is carried out under bath conditions of sufficient time and temperature to melt the core. The product is then removed and the resulting molten core is returned from the product to the bath. This Therefore, with this method, cores can be recovered more cleanly and efficiently than molded products. as well as being simultaneously collected into the molten mixture, thus replenishing the bath and adding additional cores. It allows for further use in manufacturing. Therefore, the method of the present invention apart from requiring special equipment to recover salts from water, dissolution or mechanical shaking This eliminates the need to move or separately recover core material. The present invention also provides melting (mel) The bath for the purpose of maintained at a different temperature (usually e.g. 50°F lower) to minimize the possibility of It is intended as a preferred example. The core material used in the active materials such as sand, especially foundry sand, and particles of aggregate, and also glass fibers. , glass beads, carbon fiber, plastic fiber, metal fiber - may include calcium silicate, pumice, mica flakes, and similar inert particles. The core provides structural strength to solid core materials and selected blends and mixtures of such materials. (compressive strength, shear strength, tensile strength). Sand is office or other inert material is a preferred inert material to be mixed with. In the following description, inert materials are sometimes is described as sand, but for purposes of this invention other inert materials may be substituted for or mixed with sand. can be used.

In another aspect of the invention, the bath is initially filled with the desired relative percentages of The dry premixed combination of inert particles and salt is melted and the desired physical and process characteristics. This is the time to construct the bath, and Even more importantly, make up material It eliminates any need to carefully mix the two main ingredients when added. Therefore , especially in the method of continuously molding products, even if it is expanded, one part during the original process This guarantees a substantial match from one core to another.

detailed description For drawings, inert coated solidified salt core or molten salt mixed intimately The core is formed by forming a moldable material around a core mold made of particles of the material. The method according to the invention for producing hollow molded articles consists of the following steps: ^, Mixing the particles and salt (step 12), heating ( Step 10) Prepare a bath by Step 14) is formed from a portion of the molten bath mixture and cooled to solidify the formed core; C1 Formable material (Step 16) to solidify the formable material around the resulting solid core. pressure molding to produce a solid, structurally rigid molded article containing a core; 0. The formed product (step 18) is then placed in or on the molten bath to remove the product from the product. sufficient to melt and recover the core (by gravity flow with agitation if necessary) into the bath. However, the core is heated at a temperature that is insufficient to have a negative effect on the product, causing the core to disappear. ; After that, the product is washed to remove any residual salt and/or sand (Step 2). 0).

As indicated, sand is used as core material for the purposes of the present invention.

In a preferred embodiment, the particle size is fine enough to be molded, preferably 4 Washable mensch size of 0 to 500, more preferably 80 to 100 Use foundry sand. Also alkali metal nitrates, nitrites, chlorides, carbonates, sulfates , using a low melting point salt mixture which may consist of phosphates. Preferably alkaline metal nitrates and/or nitrites such as sodium nitrate, potash and sodium nitrite, a mixture consisting of potash and sometimes with one or more alkali metal chlorides use. Eutectic salt mixtures are preferred.

commercially available grades, especially classified temperature grades. Compounded to melt at a specific temperature within the range of Granulated salt mixtures are suitable. In a preferred embodiment, the core material is reinforced. one or more alkalinizing salts or agents, such as alkali metals or is an alkaline earth metal hydroxide or carbonate, preferably sodium hydroxide or calcium hydroxide. Contains up to about 5% by weight of umum. The alkalizing agent is a It appears to serve to advantageously strengthen chemical bonds. Core material is anhydrous or contain water in small amounts, such as from 1 or 2% to about 10% (by weight) or more. There are things to do. For purposes of this invention, "low melt" refers to products that readily melt into the melt bath. A coreless mold that produces core material when configured as an intact core mold in The material is selected so that it can be melted away from the product in such a way that it recycles without adversely affecting the shaped product. The separated salt mixture is called. A preferred sand-salt bath mixture is about 250"F to 600" Items that melt at temperatures above °F5 It is. The mixture of inert materials and salts will vary in composition, preferably about 4 Contains 0-60% by weight of inert materials. As detailed below, the mixture is It is placed in a heated vessel, such as a commercial heat treatment furnace, and brought to a molten state for casting purposes. Mixed The mixture is kept relatively homogeneous by a mechanical stirring device selected from any of a variety of commercially available types. kept in good condition.

Material is extracted from the melt as needed to form a core of desired size and shape. used for According to the teachings of Weaver Patent No. 3,692,551. For example, such cores are preferably made by molding a molten salt-sand mixture into a hinged mold. It is manufactured by casting using a ged mold. Then during The child is a moldable material (+noldable material), such as metal, heat Compression molding or injection molding of plastics with or without plastic or thermoset fillers molding equipment (for discussion of suitable plastic and compression molding equipment, please use this as a reference) Added to I'1astics+6th Ed...Van No5tran d, New York+ 1981; Modern Plastics E ncyclopedia, 19'82-1983, McGraw-11+ 11.1982). If there is, To facilitate molding, a barrier coating (b) is used to help coat the salt core prior to molding. using arrier coating) or liquid clay ('5lip) is desirable. For this purpose, the salt core is coated with a lubricant paint, which makes it compatible with injection molding. It forms a smooth surface and prevents erosion of the salt core. Various coating materials include silicone, dissolved in mineral spirits (e.g. 3 to 5 layers of paraffin) When applied with a wet film such as wax or heavy oil and air dried, it will dry smooth and hard. Materials that leave a hydrophobic surface that dries are suitable. Paint forms a smoother and better inner surface Not only does it give a good impact on the part, but it also helps to produce low core breakage. There are various types of cores. For types of metal casting and plastic molding, special Softening point or degradation point of plastics ) has a melt-out temperature sufficiently lower than molded plastic products are adversely affected by the molten state in which they are used. Not heard. Core selection will vary, but -g is a typical melt cycle time; For example, in 2 to 5 minutes, the melting temperature is the critical temperature of the plastic product undergoing core removal. at least about 50 degrees Fahrenheit. During the pressure molding process, the core is the mold held in place so that the mold material under compression substantially surrounds and captures the core. , then becomes structurally rigid. According to an example of the invention, it has an intact core. These finished products must be processed for a sufficient time to effectively melt the core material from the product. In step (18), the material is immersed in a source bath, i.e., positioned within the bath, and the material is can be refilled or collected directly back into the bath without the need for extraction, mechanical vibration or other collection processes. do. In other instances, the finished molded product having an intact core therein is not in the bath; When the core is melted (by the means currently described), the meltable core material Gravity causes the core material to flow and fall into the bath, thus further advancing the core material. It is placed above the bath so that it can be collected for work. In this example, the core Heating of the product for melting is done by radiant energy, preferably in a zone above the bath. This is done by microwave heating.

As shown, during the forming step (16) and before the melting step (18), the molded product is Structurally rigid (i.e. assembled or hardened or partially hardened). as shown a melt bath (step 18) or a microwave band or similar melting process as described above; The zone shall be kept below a temperature that may unduly soften or melt or otherwise adversely affect the molded product. It will be done.

The product is then subjected to a step (20) to remove any traces of salt or sand from it, if necessary. Washed or washed away. A small amount of the sand-salt mixture is used if the core is extracted or destroyed. Although this amount is much less than being lost or disposed of, 7 lost during the course of the process, for example when casting cores and in the dip melting step (18 ) and the cleaning step (20).

In a preferred embodiment, step (10) ensures uniformity of the core composition and removes sand and salt. drying sand and granulating sand to eliminate the need to measure and mix amounts of each. The mixture is packaged in bulk, preferably for shipping and storage. Packaged in small hacks (eg 50 bonds). Therefore, in working situations, pre-mixing One or more hacks or partial banks of material are placed directly into the bath (step 12) for refilling. Advantageously, it can be added directly to the bath or used to initially form the bath during start-up. It is.

The present invention and the best mode for carrying it out will be illustrated by the following examples.

Example 1 The premix to be dried contains washed foundry sand (55 parts by weight, 80~1.OO Mesos, W edron C-30 sand) and granulating salt (27 parts sodium nitrate, 18 parts potassium nitrate) ). Generated, packaged in shipping hacks (50 lbs. capacity) The dry blended premix has no appreciable particle desegregation. Suitable for shipping and long-term storage without egregation. Approximately 430 Premixes that can be melted at °F have an effective working temperature of about 470-480 °F or higher. It can be used to produce molten salt baths that work at high temperatures. Bath equipment (15 inches deep x straight) 15 inch diameter jacketed resistance band Add 100 pounds of the sand-salt premix to a heated steel pot. Add. The bath is heated to melt the premix, and the molten bath mixture is approximately 480° Durable air motor agitation device that maintains a temperature of F and keeps the sand uniformly dripping. Stir at rest. For core molding, a split mold with a shape surrounded by straight lines is used. . High-volume aluminum molds can be quickly opened by spring-loaded quick-opening hinges. It is designed to be opened and closed. With pressurized hot water (230°F) circulating according to the molding model number. Be surrounded. For core forming, the molten bath mixture is placed in an open top of the mold from a preheated ladle. It is gravity fed into the mold by injecting it into the holes (gate holes). Filled like this The mold is allowed to cool for 20-25 seconds, then opened and molded. The removed core portion is removed and retained for transfer to compression molding equipment. Typically, The shapeable core part is uniform and very smooth.

The compressive strength at room temperature and 330.0F is 2Q, QOOps+ and 6.00 respectively. 0psi or more. The core is remelted at 475-480°F for 2-5 minutes.

A molded core section produced as described above and held at 330°F is removed from the core mold. It is transferred to a mold cavity of an injection molding machine. 330°F temperature and a thermosetting phenolic resin heat material at a pressure of 15,000 psi ( ResinRXx660, RogerS+ Go, Manchester, Conn, ) is then injection molded into the mold cavity and around the molded salt core.

After 30 seconds, the resulting phenolic resin molded product is fully polymerized and solidified. It is cooled in the mold and becomes structurally rigid. Moldable plus with intact salt core The tick product is then removed and soaked in the salt bath mixture held at 480°F for 2-5 minutes. be done. While soaking, the product should be considered for good drainage just as it is removed. is maintained in the correct position. During the melting period, the salt core completely melts, so the plastic 9 When the product is removed from the salt bath mixture, any remaining molten salt core material is immediately removed from the product. Discharged to the bath for bath replenishment. Any traces of salt or sand left on molded products can be washed away with water. It will be done.

Example 2 50% by weight washed foundry sand (80-100 mesoyu, Wedron C-30 sand) , 48% granulated salt (sodium nitrate, sodium nitrite, potassium nitrate, 30:20: 50) and 2% of Chosobud glass fiber to produce a dry premix. do. Packed in a shipper bag (50 bond capacity) Additionally, the resulting dry compounded premix can be shipped and stored for long periods of time without significant particle segregation. Suitable for storage. A premix that melts at about 350°F is about 350-380°F It can be used to produce molten salt baths operating at effective working temperatures above. Bath equipment (deep 15" x 15" diameter jacketed resistance band heated steel pot) 100. Add 1 pound of sand-salt premix. The bath will melt the premix The molten bath mixture is maintained at a temperature of approximately 350°F and the sand is uniformly suspended in a suspended form. Stir to maintain consistency. A mold like the mold mentioned above is used for core molding. Ru. The molten bath mixture is poured into the mold from a preheated ladle through an opening at the top of the mold (gate hole). gravity fed.

The mold thus filled is allowed to cool for 20-25 seconds and then opened. The molded core portion is removed and retained for transfer to compression molding equipment. Noriyoshi In terms of mold, the moldable core part is uniform and very smooth. Room temperature and 2506F The compressive strengths are greater than 20,000 and 8,000 psi, respectively. The middle child is 35 Remelts in 20-30 seconds at 0-380°F. generated as described above, and 2 The molding core part maintained at 50°F is transferred from the core mold to the mold cavity of the injection molding machine. be transferred. Commercially available polyester resin bulk molding compound (B M C% bulk molding compound) at a temperature of 280°F and 1 5. At a pressure of 000 ps+, injection molding is then carried out around the molded salt core into the mold cavity. Shaped. After curing, the molded product is polymerized in the mold to ensure sufficient solidification and structural becomes rigid. Products with intact salt cores are then removed and processed to melt the cores. immersed in a salt bath mixture held at 350°F for 2 to 5 minutes.

While immersed, the product is positioned to allow the core liquid to drain from the void in the product. The product is then washed and dried.

Examples of the above-mentioned treatments according to the invention at different temperatures with suitable moldable materials Examples are further shown below.

Brief description of the drawing The drawing is a flowchart of a configuration diagram showing a preferred example of the pressure molding method of the present invention. be.

Figure 1

Claims (1)

[Claims] 1. ^, Mixing particles of inert material with salt to produce a homogeneous molten bath mixture , prepare the bath by heating;B. formed from a portion and cooled to solidify the formed core; C1 Formable material is pressurized around the resulting solid core to solidify the formable material. shaping, thus producing a solid, structurally rigid molded article containing a core; and is sufficient to melt and then recover the core from the product into the bath, but placed in or on a molten bath at temperatures insufficient to adversely affect the product. The process consists of heating the molded product until it is thoroughly mixed with molten salt and covered. A coagulating salt core made of particles of inert material or a moldable material around a core mold. A method of manufacturing molded products by forming. 2. Salts include sodium nitrate, potassium nitrate and optionally sodium nitrite). The method described in box 1. 3. Melting of foundry sand and core molding salt which can be granulated in an amount of about 40 to 60% by weight of the sand. A medium for use in the compression molding method according to claim 1, comprising a dry mixture to be blended. Premixed composition for producing child molds. 4. The mixture contains about 2.7 parts by weight of sodium nitrate and about 18 parts by weight of potassium nitrate. The composition according to claim 3. 5. Prior to pressure molding, the core mold to be solidified is coated with a lubricating film made of hydrophobic lubricating material. 2. The method according to claim 1, comprising the steps of: and drying the film. 6. From an unmolten blended dry mixture of inert materials and granulatable core molding salts. A premix assembly for producing a core mold used in the compression molding method according to claim 1 A product. 7. The premix composition of claim 6, wherein the inert material comprises sand. 8. The premix assembly according to claim 6, wherein the inert material is glass fiber. A product. 59. The premix according to claim 6, wherein the inert material is carbon fiber. composite composition. 10. The premix composition of claim 6, wherein the inert material comprises mica flakes. ■