JPH06509125A - How to dry microspheres - 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] How to dry microspheres Summer Background of the invention A Preface The present invention provides a method for drying and optionally drying thermoplastic resin microspheres. Regarding foaming.

This application is filed on March 8, 1990, in the applicant's pending U.S. Patent Application No. 7 490. This is a partial continuation application of No. 332, 3511. s. c. +20 We hereby claim the profits based on the provisions of.

Microspheres are hollow spheres of heat-expandable thermoplastic polymer containing a heat-activated blowing agent. . Much information about such substances, their production methods, physical properties and uses of microspheres No. 3, previously granted to Donald Niss Morehouse. 615, It is all described in No. 972. There are other examples of such substances and uses. For example, U.S. Pat. No. 3,864. No. 181, No. 4, No. 006, No. 273 and 4th. 044. No. 176 teaches.

According to the teachings of the Morehouse patent cited above, microspheres have a limited agglomeration method under pressure. The resulting product consists of unexpanded microsphere beads and a wetting agent. It is a "wet cake" consisting of water and water. The solids content of this wet cake is typically of about 40 to 75 percent by weight, and the process of using a wetting agent in this bead formation. The reason is to moisten the surface. Many important uses of microspheres include Removal required.

The beads are usually foamed before use. In unfoamed form, dry microspheres It typically has a displacement density of about 1.1 gCm3. dried and foamed microspheres The body typically has a displacement density of less than about 0.06 g,'cm3, and is It is very useful in the production of Nantakutinoku foam in the mer matrix.

Free-flowing expanded microspheres are now commercially available for this and other uses. Achieving the evaluation and market requirements.

B. Conventional technology Until now, almost no method was known for producing foamed microspheres from a wet cake. Ta.

Conventional techniques for producing foamed microspheres require that there is residual moisture in the product or , foamed beads are produced in dry form with a significant amount of agglomerates and limited degree of expansion. It is limited by at least two points: Achieved through this process An "acceptable" level of agglomeration is in the range of about 3 to 10% of the product.

In U.S. Pat. No. 4,397,799, pre-foamed dry low density microspheres The bodies are manufactured by spray drying. This spray drying has several drawbacks. first Most importantly, it requires the selection of dedicated spray drying equipment and requires a significant capital investment. and especially because of the cost of skilled labor and equipment to heat the drying liquid. This requires an extremely large amount of working capital. Also, the product is heated produced in a moving liquid stream that requires considerable collection, recovery and handling. be done. In addition, because of the size and cost of the equipment, it is not possible to produce the foamed product just before use. It is impossible to realize this with a general I-co, and the spray drying method is very difficult to transport in large quantities, which is expensive. I am given a lot of responsibility. The requirement that spray drying be carried out under an inert atmosphere cannot be ignored either. do not have. This is because ordinary blowing agents contained in microspheres are generally flammable and often Although often explosive. Typical processes use nitrogen as the spray drying fluid. Although this is necessary, it is a very expensive burden on system safety. Ru. Recovery of expanded beads from this system is also required. This reduces product loss Not only to avoid, but also because of the resulting working environment and atmospheric dust pollution. be. In addition, spray drying techniques require approximately 0. less than 32g/cm' up to about 0.40 gcm', typically about 0.40 gcm'. Foaming density of 36g7cm” Experience has shown that it is suitable for lathering. Trials at lower densities An unacceptable level of agglomeration of more than about 10% of the product and an equally acceptable resulting in excessive foaming and consequent product loss due to rupture of the bead structure. It has become a fruit.

Foaming of microspherical beads is carried out using a wet case 1 according to the method of U.S. Pat. No. 4,513,106. This can be achieved by introducing into a steam stream followed by quenching with cold water. This results in A prefoam of microspheres is produced, which is still wet with water (7). Low solids content. Products with a solids content of 15 percent are sometimes obtained. , the solids content of typical products is often about 3 to 5 percent. this water This limits the range of applications in which this method can be applied.

No. 4,722,943, the disclosure of which is incorporated herein by reference. However, the inventor has developed a method for processing wet cakes using processing aids in a consistent operation. A method of mixing, drying, and foaming is disclosed. In that invention, the processing aid bonding, i.e. the surface of the microsphere is heated to a temperature higher than its glass transition temperature, T. by acting as a hot melt adhesive that binds the polymer with its processing aids. , it comes into close contact with the surface of the microsphere and is embedded within it. , required for operations like the second The equipment is quite substantial, the process is difficult to control, and it is difficult to maintain product quality and uniformity. difficult to maintain. If carefully controlled, the degree of product aggregation can be It is within the range of 3 to 10%, which is the limit considered "acceptable". Inventor The patented process requires invested capital and working capital to achieve acceptable product quality. Although we have achieved cost reductions, we need to further reduce costs and further improve quality and productivity. desirable. In addition, the degree of foaming of microspheres can be made larger, and this method depends on Adhesive surface-blocking liquids or mixtures of such liquids and solids may be used. It is desirable to make it as low as possible. Experience shows that microspheres account for more than 30% by weight of the mixture. When necessary, agglomeration can be avoided to an acceptable level by increasing the proportion of microspherical beads. I found that it was becoming difficult to do so. This may be caused by a surface blocking liquid or products with the lowest proportion of mixtures of liquids and solids and the lowest density of composite materials, such as This is a serious problem because it is a more desirable product in major applications.

No. 07/490.332, the disclosure of which is incorporated herein by reference. However, the present inventor has developed a drying and foaming technology for thermoplastic resin microspheres. Disclosed and filed a patent claim. The present application provides further improvements to the drying and foaming operations disclosed in said application. With respect to the development of It is a liquid substance at drying temperatures.

C1 Purpose of invention One object of the present invention is to provide a continuous drying method for thermoplastic resin microspheres. An object of the present invention is to provide a method for removing water from plastic resin microspheres.

Another object of the present invention is that substantially agglomerates and An object of the present invention is to provide a method for producing microspherical beads that do not contain water.

A further object is to continuously dry and optionally foam microspheres from a wet cake. It's about giving your body.

reasonably expensive in investment and operation, and economical in terms of the use of its products. A method that has a level of utility value and can be operated with moderate labor and equipment costs. Dry, moisture-free, optionally foamed microspheres can also be provided. This is the object of the present invention.

The object of the present invention is to develop a free-flowing, optionally foamable material with exceptional and unique properties and characteristics. An object of the present invention is to provide microspheres that are

■Summary of 0 invention In the present invention, dry microspheres are combined with a surface-blocking liquid or with such a liquid and a solid material. with an adhesive coating consisting of a mixture of Low density of up to 0.020 g/cm' and agglomerates in the product rates) is generally less than 1% of the product, often less than 0.1%. Dry and optionally foam by a method that can be reduced by.

The method of the present invention involves first injecting dry microspheres into a surface-blocking liquid or such a liquid and a solid. Mix with the material and then dry the microspheres to remove water and surface barrier The surface of the microsphere is coated leaving behind a liquid or a mixture of such a liquid and a solid material. It is based on sequential or simultaneous steps of coating. Sequential microsphere Or simultaneous foaming is facilitated.

Development of the advantages of using surface barrier liquids or mixtures of such liquids and solid materials See the lowest level of surface-blocking liquid or mixture of such liquid and solid material. Excellent physical properties, especially agglomeration, while maintaining high product quality, even in This results in a decrease in lomeration. Coagulation occurs in the foaming process. It does not occur to any substantial extent. Surface blocking liquids or such liquids and solids Free-flow foamed microsphere product by controlling the proportions of the mixture with the material components It can be made into a mobile powder, compacted powder, or a cohesive flowable aggregate.

■Summary of 9 drawings FIG. 1 is a schematic illustration of the microspheres of the present invention after drying, and shows a surface-blocking liquid or shows a microsphere with a thin film of a mixture of liquid and solid material attached to its surface. ing.

FIG. 2 is a schematic diagram illustrating the drying process of the present invention, as described in Example 1 below. It's Low Dia Dalam.

■Detailed explanation The most common use for expanded microspheres is as a syntactic compound in a polymer binder system. Blending as an ingredient in tic foam formation. exceptionally low Density properties are important in applications where the relationship between weight and volume of such materials is considered. brought about great changes. As a general rule of thumb, add 1% by weight of expanded microspheres. This results in a substitution of about 20% by volume in a typical system.

The properties of microspheres have hindered many studies on their drying and prefoaming. . Severe agglomeration and transfer of material to the warm surfaces of the equipment Adhesion has prevented most research into such procedures from serious considerations. vapor Wet foaming eliminates applications where aqueous systems are not desired and spray drying processes are too costly. product is prone to excess, extremely difficult dust problems, and considerable agglomeration and Limited foaming of beads, these factors are limiting the effective development of the major market. Ta.

Traditionally, the generation of agglomerates is an inevitable consequence of microsphere foaming. It was considered a fruit. Even by the procedure of the inventor's above-mentioned prior patent, foamed beads It is believed that it is necessary to tolerate about 3 to 10 percent of aggregates in the Higher degrees are common in some conditions. However, the inventor now The main factors responsible for the formation of agglomerates are the characteristics of the wet cake and the conventionally used It has been found that the deficiencies of the foaming and wetting process should be found. The inventor has Moisture is applied to ensure complete separation of beads prior to foaming to reduce agglomeration. I learned that Jun Cake requires a considerable level of mixing during the process.

Substantial mixing with surface-blocking liquids or mixtures of such liquids and solid materials is important. The inventor's discovery that there is, means that sufficient mixing is done prior to foaming. and lead to other discoveries and considerable benefits achieved in the present invention. These are below It will be explained in detail later, but it can be summarized as follows.

1. Foaming to the lowest density ever achieved is possible in liquid-based systems. It became Noh. The density of these microspheres is less than 0.03 g/cm", often 0.03 g/cm". 02 to 0.015 g/c+o''.

2. Without creating agglomerates in the product, Low proportions of surface-blocking liquids or mixtures of such liquids and solid materials may be used. can.

3. Precise control of bead foaming is achieved, resulting in under-foaming, over-foaming and breakage. The percentage of beads decreases.

4. Process control conditions are simpler, equipment requirements are less stringent, and product Simple control with inexpensive equipment while achieving higher levels of quality, uniformity, and productivity. It can be operated according to your conditions.

5. The amount of aggiomerates is consistently less than 1% of the product; In many cases it is kept below 0.1%, so that subsequent generation is required to separate the aggregates from the product. Foam processing can be removed.

6 Very low levels of overexpanded beads, broken beads, and bead debris Post-foaming processes to separate mer fragments and other dense parts can be eliminated.

7. Liquid surface barrier coatings facilitate sequential or simultaneous compounding operations; It is faster to mix the microsphere component into the formulation to create a homogeneous dispersion of microspheres. , can be achieved more easily and more reliably.

8 When a blend of both liquid and solid particles is used as a surface barrier coating, , can offer a unique combination of physical properties.

9. If the surface barrier liquid is reactive in the subsequent formulation, the final product The physical properties of the composition, especially impact strength and tear strength, are often considerably increased.

10. The overall effect of all of this is to increase manufacturing costs while substantially increasing product quality. It is possible to reduce costs and obtain a wider range of products than previously available.

Surprisingly low weight ratios of surface barrier liquids can be used, which reduces the Prevents agglomeration of microspheres during foaming, and It has been observed that such substances actively and effectively suppress the dusting of foamed products. It was. The combination of this feature and observation suggests that the microspheres are first placed in a surface-blocking liquid or The mixture of liquid and solid material is mixed until the bead surface is completely wetted, followed by Development of effective foaming of microspheres by controlled drying and product recovery led. The microspheres remain in the desired closed cell state and avoid undesired agglomeration. It is substantially free of agglomerates. sequentially or simultaneously The biofoaming is higher than the limits established by previous efforts in this field of technology. carried out to the limit. That is, less than 0.03 g/cm", 0.015 to 0.0 Microsphere densities as low as 2 g/'cm' are achieved.

In the present invention, for most applications of this microsphere, volume is often considered. It is particularly important that even if the proportion is quite significant on a weight basis, it is It is important that the component be negligible or very trivial. For example, surface blocking Using DINP (di-isononylphthalate) as the liquid The volume and weight of dried foam microspheres by varying the amount of DINP were The relationship between amounts is shown in Table 1.

Tojo table Foamed microspheres blended with DINP Product microsphere content 90 99, 8 0.022 80 99, 5 0.025 70 99, 1 0.028 60 98, 6 0.033 50 98, OO, 039 4097,OO,048 3095,40,064 2092, 30,092 1084, 40,169 Note: This data is based on microspheres of 0.02 g/cm3 and 0.965 g/am3. Based on DINP.

As shown by the relationships in Table 1, even if the weight ratio of DINP is very large, foaming will still occur. Changes in the volume of objects are slight. In particular, there are many polypropylenes involved in this microsphere application. It is possible to find these substances in polymer systems as extremely common plasticizers. Therefore, it is usually preferable to use such materials as surface blocking liquids in the present invention. Delicious. In many cases, surface-blocking liquids or mixtures of such liquids and solid materials are It is advantageous to mix them with one another or to use them in combination.

In most applications of expanded microspheres, such materials are It is a constituent of the formulation planned by the user.

And when such ingredients are added to the formulation, the increased amount included along with the microspheres. It is simply necessary to make a significant amount of adjustment to compensate. wide variety Such materials meet the functional requirements of the present invention and are suitable for use in almost any environment. Surface barrier liquids or combinations of such liquids and solid materials that meet the end-use formulation requirements. A mixture of can be found.

Appropriate levels of such surface-blocking liquids prevent microspheres from agglomerating and drying. It effectively eliminates the tendency to stick to the heated surfaces of the foaming machine and also improves the final foaming Dusting of foam products can also be substantially reduced, if not effectively eliminated.

Flame retardant surface barrier liquids or mixtures thereof that are flame retardant under the conditions of operation and working characteristics. The selection of certain materials allows for Allows for effective sequential or simultaneous foaming at temperatures that do not require an active atmosphere. It became possible to use a device that This results in a significant reduction in manufacturing costs and It means truly achieving system safety. Bees manufactured according to the present invention are normally dusting-free, and are designed to reduce dust-related hazards. No inert atmosphere or other processing equipment is required.

Although it is generally preferable to avoid flammable materials whenever possible, appropriate safety precautions should be taken. Of course, if necessary, combustible materials should be removed with a surface barrier liquid, provided that safeguards are used. It may be used as a body or as a mixture of such liquid and solid materials.

As the person skilled in the art is already aware, the method of the invention and the products produced according to the invention There are a considerable number of parameters governing the Their important parameters are listed below. This will be explained in sequence in relation to the details.

Microspheres are generally available as wet cakes. That wet cake is typically is about 40% water, about 60% unfoamed microsphere beads, and the composition of the Morehouse patent. It consists of trace amounts of substances, or wetting agents, used in the production of beads by the method.

The most readily available microspheres are from the New York State 14240-1092 bag. Farrow, P.O. Box 1092, 710 Ohio Street Pier Pierce & Stevens Corp. ration), and they are mainly used as blowing agents. Polyvinidene chloride microspheres containing sobutane. How many microspheres are currently available? It contains a small proportion of comonomer in bead polymerization. Above available In the present invention, substances capable of stomach. Copolymers generally have higher Tg and foaming temperatures.

As the Morehouse patent above shows, microspheres can be used in a rather wide variety of thermoplastic materials. Can be made from polymers. In fact, commercially available microspheres are nylidene, or a random copolymer of vinylidene chloride and acrylonitrile, or Random terpolymer of vinylidene chloride, acrylonitrile and divinylbenzene almost limited to. polyacrylonitrile, polyalkyl methacrylate, poly Microspheres of other materials such as styrene or polyvinyl chloride are also known; These materials are not widely available. The present invention forms microspheres. It can be applied to any thermoplastic resin. However, polyvinylidene chloride is used as the basic material. Since microspheres are the most readily available in the industry, the discussion will primarily focus on these materials. Now. As those skilled in the art are already aware, processing parameters can vary depending on the polymer material. Adjustment is required for use in

Various blowing agents can be used in the microspheres. Commercially available products are more limited in scope. and often from lower alkanes, especially propane, butane and mixtures thereof. , the one suitable for the polyvinylidene chloride polymer is selected. Morehau above As the US Patent clearly states, the choice of blowing agent depends on the thermoplastic polymer used. and, for this discussion, are commonly used with commercially available microspheres. The greatest concern is paid to blowing agents. Polyvinylidene chloride microspheres contain Sobutane is most often used.

In unfoamed form, microspheres are formed into various sizes and are readily available on the market. Most available are 2 to 20 microns, especially 3 to 10 microns. these When foamed, these materials often have bead diameters from IO to 100 micrometers. Ru. It is also possible to manufacture microspheres in a wider range of sizes, and the present invention The same applies to these. For example, the diameter of microspheres before foaming is approximately 0.1 micron. This proves that it is possible to manufacture anything from as small as 1 millimeter to as large as 1 mm. It has been made clear. Such materials are not normally available.

Available microspheres are characteristically spherical, although a variety of shapes are possible; The foaming agent is located approximately in the center of the cavity.

Dry, unfoamed microspheres are typically slightly larger than 1 g cm has a displacement density of about 1.1 g/cm'.

When such microspheres are foamed, they have a diameter of 5 to ro ( 6 in diameter, less than 0.1 when dry, often about 0.03 to 0. resulting in a displacement density of 0.06. In the present invention, 0015 to 0,020g, ・cll It is possible to achieve foam densities as low as 1.

Since the microspheres are manufactured in an aqueous suspension, this suspension is broken and dehydrated to remove the solid content. It is common to supply the microspheres in the form of a 60% wet cake. child This avoids shipping larger than required quantities of aqueous systems.

The solid content of the wet cake is essentially all unfoamed microspheres, but may contain a wetting agent. It is difficult to remove residual water from the wet cake as it also contains suspended components. Have difficulty.

Drying work is carried out using a conventional contact type indirect heat exchange stirring dryer with high speed and high shear capacity. It is conveniently done using Various types of equipment are available. In general, arbitrarily reduced Good temperature conditions with rolling operations, good mixing of powder and granular materials, high shear stress requirements for removal and recovery, preferably with condensation of evaporated water. be. Active cooling of microspheres can be carried out both in the agitator dryer itself and in attached equipment. is also done voluntarily.

Most applications meeting the aforementioned criteria are capable of batch or continuous operation in connection with the present invention. A wide variety of agitated dryers can be used in any scale operation. Typically, Continuous operation is preferred.

The surface barrier liquids of the present invention or mixtures of such liquids and solid materials are suitable for the intended function. It can be any of a variety of substances that meet the performance requirements. Surface barrier liquid or such liquid The mixture with the solid material is a free-flowing liquid at the temperature and pressure of the drying operation. bodies or mixtures of such liquid and solid materials, microspheres, and preferably Other components in the system, such as wetting agents and related components in the wet cake, are removed during the drying process. Microspheres that do not chemically react at temperature or pressure and are in the process of foaming at the foaming temperature It is required to function to separate bodies so that they do not touch or combine with each other. Ru.

Surface barrier liquids or mixtures of such liquids and solid materials meet the following general characteristics: selected from one or more components.

Surface blocking liquids or mixtures of such liquids and solid materials can be used to form thermoplastic microspheres. Must be a non-solvent for the polymer, preferably by swelling the polymer in the microspheres. Must not be.

The liquid must freely wet the surface of the microspheres.

The liquid will not polymerize under the mixing, drying, handling, packaging or storage conditions used. Do not oxidize, decompose, or undergo any other reaction. however , the liquid-bead composite chemically react or physically transform in subsequent formulations in which it is incorporated. It may be a substance selected for this purpose.

The liquid can be dried at any convenient temperature at which the water has a substantial vapor pressure. The temperature of the drying step is preferably at least about 100°C, preferably at the onset of bead foaming. temperatures below the Tg of the microsphere polymer (both 20°C below the melting temperature). Must have points.

If the surface barrier liquid has a melting point above ambient temperature, it may be coated and dried. Preferably, the first microspheres are cooled while being mixed under shear stress, and the granules are produces a similar product.

In addition, the liquid has a drying process and a sequential or simultaneous foaming process) It must have a high, preferably substantially high, boiling point.

Select an appropriate table from a variety of materials that meet the general characteristics required for such materials. The choice of surface blocking liquid will generally be consistent with the procedure and intended use of the product. It is a problem of balancing the many functional demands of Among the criteria to advise those skilled in the art There are the following:

The primary function of a surface barrier liquid or a mixture of such a liquid and a solid material is to prevent the microspheres from coming into direct contact with each other and the surface of the processing equipment, and prevent them from coming into close contact. The goal is to prevent people from wearing their clothes. The barrier coating material absorbs heat by wetting the surface of the microspheres. The barrier between the plastic material and any other material it might otherwise come into contact with form the rear.

When the invention is being implemented for a particular known end use, surface blocking Tailoring the selection of liquids or mixtures of such liquids and solid materials to the requirements of the application. is usually possible. surface barrier liquids or mixtures of such liquids and solid materials; It is common to consider desirable. As those skilled in the art will already recognize, surface blocking liquids or such The fact that mixtures of liquid and solid materials adhere closely to the surface of microspheres indicates that their factors that require adjustment of the Not.

Combinations of different substances can be used as surface barrier liquids or mixtures of such liquids and solid materials. When used as a product, it is possible to stay within the formulation requirements of virtually any design recipe. is possible.

The surface barrier liquid or a mixture of such a liquid and a solid material may be cohesive (cohesive). Due to its siveness, the composite product is resistant to air currents or environmental atmospheres. Greatly reduces the tendency to be carried around. As already understood by those skilled in the art, milling The dusting tendency is important both in terms of worker exposure and in terms of fire and explosion hazards. It is a cause of impairing material safety. The microspheres contain a substantial proportion of an alkane blowing agent. Therefore, large amounts of these substances in the atmosphere may pose a real problem in some situations. It is. These difficulties and the effort and expense to solve them are not included in the present invention. being reduced or eliminated.

Thanks to the composite's increased cohesiveness, foaming The requirements for processing equipment and systems when recovering dry microspheres are very simple. and product loss is substantially reduced.

The microspheres are homogeneously dispersed in the liquid in the composite product.

In most environments, dry microspheres have a surface barrier liquid with a melting point above ambient temperature. Otherwise, it will be in a relatively dry, free-flowing granule state. If the surface barrier is at ambient temperature When the ratio of liquid to microspheres is relatively high, It becomes a sticky, flowable, floc-like mass. The proportion of surface blocking liquid is When relatively low, the mass is loosely organized, somewhat granular or powder-like in character. The clamps are in relatively tight contact with each other. ent) remain as is. Such [granular floc s) J is used in solid handling and processing equipment, such as wet powder or granular materials. It also allows for handling of composite materials and provides additional dispersion formulation benefits. Therefore, multiple These shapes of composite materials are generally preferred for most applications. Usual In proportions, the mass of the dispersion as described herein will depend on the particular liquid used. It shows the viscosity. Flocholeicidin (flocculation) is a microsphere. occurs without agglomeration (aggloIIleration), and the microspheres are individually remain in a separate state that can be distinguished from each other. Microspheres are generated sequentially or simultaneously. Even when foamed, all the above properties are retained.

The flocculant-like action of the surface barrier liquid Thanks to the cohesiveness provided by Even low percentages of surface blocking liquid greatly reduce product dusting . In addition, these similar properties are achieved with a much lower proportion of surface barrier materials compared to solid particles. drying of microspheres at even lower densities than previously achieved. Enables effective production of composite materials. Therefore, syntax made from this composite material Chick frames have the potential for lower densities.

The surface-blocking liquid wets the surface of the microspheres while the composite material When a liquid (ite) is incorporated into a polymer system, the liquid is often mixed into the system. dissolve or disperse in The surface of the microsphere is then squeezed by the surface blocking liquid. The final formulation becomes more homogeneous as it is wetted with the final formulation. For example, In tactical form, compressive strength, compression set, impact strength, some or All tensile properties are improved. Non-tactic foam product is adhesive When the adhesive strength is increased significantly.

These properties are not lost when solid particles are used with surface barrier liquids. Main departure Unlike Akira's previous results, in this case the solid particles are bound to the surface of the microsphere. rather than becoming dispersed within the binder matrix in the formulation. Usage The solid materials to be referred to have been previously cited and discussed and are incorporated herein by reference. This is described in the inventor's earlier application.

The selection of the surface barrier liquid, and optionally the solid particles, determines the optimal should be based on the end use and should preferably be included in the planned formulation. It is a good ingredient. The liquid is preferably a functional component of the product. To be elected The liquid substance preferentially wets the surface of plasticizers, surfactants or microspheres, for example. Wetting agents, bulking agents or diluents, for ingredients of the formulation (rather than the microsphere solvent) solvent, reactive monomer, oligomer, prepolymer, or low molecular weight polymer, or It may be a polymer solution or a non-aqueous dispersion. Other similar substances are usually It can be used among the many substances used in compound formulations.

A feature of the present invention is that the ease of handling of solid materials is combined with the ease of blending and mixing of liquids. It is that it has been combined. As a result, the microsphere component has the ability to easily mix liquids. This makes it very easy to work with, as it is easily dispersed into the formulation.

When a polymerizable or crosslinkable liquid is used, it is possible to create another liquid by polymerizing or crosslinking. An advantage of the present invention is to provide individually discrete microspheres coated with other polymers. A deformation will be obtained. Polymerization reaction or crosslinking reaction is a condition for microspheres to foam. or, if desired, at a low temperature where the microspheres remain unfoamed. It's okay to be. Strong exotherms should be avoided, as temperatures leading to the collapse of the microspheres should be controlled to avoid overheating. This selection provides exceptional solvent resistance. Microsphere products can be produced that exhibit properties and heat resistance. This kind of technology When used, the microspheres are usually not bonded to each other by reaction and are in an independent form. It is preferable to include solid particles within this liquid to ensure that stomach.

When such polymerization or crosslinking reactions are used, thermal activation or catalytic Addition polymerization or condensation polymerization or crosslinking reactions can be used; is in an air atmosphere, in an inert gas atmosphere, and in the presence of a solvent or dispersion medium. Alternatively, it can be carried out by interfacial reaction. In interfacial condensation reactions, especially liquid-liquid or Gas-liquid reactions are interesting.

This is because in these types of reactions, constituent components that may disintegrate the microspheres are The reactants can be adjusted with great flexibility while still protecting the microspheres from the effects of This is because you can make a selection.

In the present invention, the surface barrier liquid or a mixture of such a liquid and a solid material is , foaming of microspheres without adhesion to the equipment used and without the formation of microsphere aggregates. used in sufficient quantities to produce This amount requires special equipment and special processing. Depending on the conditions, surface blocking liquids or mixtures of such liquids and solid materials; In most cases, on a dry weight basis, the blocking liquid or the mixture of such liquid with solid material A range of about 5 to 97 weight percent of the compound and microspheres is used. − According to the groin, in most situations the amount used is a blockage liquid or such The minimum number of people that can reliably and consistently achieve the specified function of a mixture of liquid and solid materials. be. The blocking liquid or the mixture of such liquid and the solid material may be may be used in an amount less than 80 weight percent, preferably less than 80 weight percent. Generally preferred. This naturally means that the foamed product is greater than 90% by volume. The result is that it contains microspheres. The surface area of microspheres is quite large. Therefore, less than about 5 weight percent of surface barrier liquid will result in incomplete coverage and later problems. lead to difficulties. Generally, at least about 10 weight percent surface barrier liquid is used. It is preferable to

In most applications of microspheres, volume fraction is most important, so a surface-blocking liquid or Even if the mixture of liquid and solid material contains a very large proportion by weight, such as Many end uses are harmless. As a component of the microsphere formulation, a surface blocking liquid or If a mixture of such liquids and solid materials is introduced in substantial quantities, this composition Appropriate tolerances should be made in the formulation of materials.

If desired, use surface blocking liquid or A mixture of such liquid and solid materials may be used, but the surface of the microspheres must be It is generally recommended to avoid using too much more than the amount that actually and completely wets the product. desirable.

In the present invention, any foaming of the microspheres is carried out with the surface barrier liquid, optionally under low pressure. Or while active stirring in a mixed state with such a mixture of liquid and solid material, This is achieved by heating. Contact drying processes using indirect heat exchange are generally the most effective. However, as mentioned above, the present invention uses special and unusual conditions. shall be applied.

The foaming operation was carried out by Littleford Company, Florence, Kentucky. Blow mixers such as those available from Eford Bros., Inc.) It can be conveniently done inside. These mixers are made of microspheres and surface-blocking liquids. or at a high temperature capable of achieving complete dispersion and mixing of such mixtures of liquid and solid materials. Provides heat exchange capacity to create fresh agitation and effectively remove water from the mixture.

The mixer is equipped with an outlet for removing volatile components under reduced pressure or vacuum. It is.

In the present invention, during the mixing step and, if performed, the foaming step, the active A mixture is used. In traditional methods, in particular, the surface of the beads is To prevent the microsphere beads from breaking when heated to high temperatures to soften them. , substantial shear stresses are avoided. The inventor has discovered that the very At controlled temperatures, beads do not break even under fairly sufficient shear stress. I observed that.

The inventor has determined that this blow mixer operation is generally sufficient to remove agglomerates from the final product. observing what you do. substantially free of aggregates, i.e. 1 of the total product %, often less than 0.1% agglomerates You can get things.

The term "active mixture" as used in the present invention is a highly functional term, at least is also sufficient to remove aggregates in the dried product, but bead breakage is severe. It will be clear to those skilled in the art that this is meant to a lesser extent than that occurring. concrete The minimum and maximum values depend on the equipment used and its usage and operating conditions. There is.

Blow mixers provide very controlled temperatures throughout the process at which foaming occurs. It is operated at a degree. Once mixing and foaming is complete, add a surface barrier liquid or The mixture of microsphere beads and solid material is substantially homogeneous and substantially aggregate-free. forming a blend that does not

The microsphere component has a low density of approximately 0.015 grams per cubic centimeter. Can be foamed.

Foaming can be done in any affordable manner, in batch or continuous operation, suitable for transferring heat to microspheres. It can even be done inside the device. Surface blocking liquids or mixtures of such liquids with solid materials The adhesion of the objects is maintained at the foaming temperature and the water has already been removed, so the heat for foaming is Only requirements need to be considered and controlled.

The homogeneous blend produced in this mixture can be heated indirectly in very simple and inexpensive equipment. Foaming can be achieved with low shear stress agitation, which helps in uniform and efficient heat transfer through exchange. It was discovered that The dried beads to be foamed are already free from agglomerates. , and as long as it is sufficiently wet and sufficient homogeneity of the blend is achieved. High speed, high shear agitation is not required in this foaming operation.

Foaming can be done in a blow mixer, but it is faster and less expensive. It is generally desirable to foam continuously in the equipment, if desired. like this Suitable for use include Bepex, Inc., Loring Methus, Illinois; Soldia available from Bepex Corporation ire® continuous heat transfer device.

The foaming device must supply energy solely for foaming. this is big The bead temperature at which foaming occurs (depending on the specific polymer In most situations, achieving the desired degree of foaming There are almost no difficulties. In most situations sufficient foaming, i.e. 0.03 g/ cm', preferably about 0.02 g/am3 (surface blocking liquid or such liquid A microsphere density of (except for mixtures of solid materials) is desired.

Important temperature limitations are defined by the thermoplastic resin. Hollow spherical shape due to excessive foaming It is important not to melt the polymeric material because the structure will be lost. On the other hand, temperature is not high enough to soften the polymer and develop proper blowing agent pressure. , foaming does not occur or is insufficient. The foaming process has clearly limited Because of the time, residence time at the appropriate temperature is also a useful parameter. suitable Even when the correct temperature is achieved, if the residence time at that temperature is too short, The bubbles become incomplete. If the time is too long, the microspheres themselves will over-foam and break. It may tear apart, leaving broken spheres, polymer fragments, or grids in the product. associated with a loss of productivity. The heat transfer rate generally depends on the specific equipment used. Depending on the diameter, a residence time of 0.5 to 3 minutes is often sufficient.

The foaming temperature is generally close to the glass transition temperature of amorphous materials and the melting point of crystalline materials, but in practice It's not higher in quality. Regarding these matters, please refer to the above-mentioned Morehouse patent. is discussed in detail.

The function of the surface blocking liquid or mixture of such liquid and solid material is that of the microspheres. The aim is to prevent the formation of aggregates to the greatest extent possible. For most devices, this special requirement can be achieved using continuous low shear stress agitation of the material in a foamer. effect Targeted agitation also promotes even and uniform heat transfer to the particulate material.

The degree of foaming can vary from substantially zero to known foaming limits. This parameter - depends on the temperature, the residence time at that temperature, and to a lesser extent the pressure in the system. It is determined by

For foaming to occur, the blowing agent must develop a substantial internal pressure (compared to external pressure). and the polymer must be sufficiently soft to flow under the influence of its internal pressure. There is a point. This generally means that the polymer is heated at a temperature close to its melting point or glass transition point. or at a slightly higher temperature, typically based on polyhynylidene chloride homopolymer. This means that for the microspheres to be heated to about 120°C, . If the polymer temperature is too high, the microspheres will over-foam and burst and break. Put it away. The upper temperature limit is approximately 180°C for copolymers and about 180°C for polyvinylidene chloride. The temperature should therefore preferably be no higher than 150°C. These melts At temperatures above the glass transition point or the glass transition point, the residence time at that temperature is short. It should be.

The temperature increases to the point where the microspheres soften and begin to foam, and their surface areas When becomes viscous, the surface-blocking liquid or mixture of such a liquid with a solid material Wetting the surface and preventing agglomeration and good agitation will help the microspheres form at that stage during this process. operates to maximize the amount of heat transfer to. The degree of stirring is narrow and not limited. , with its agitation, the surface-blocking liquid or a mixture of such liquid and solid material and the microscopic A uniform, substantially homogeneous blend of spheres is maintained, resulting in relatively even heat transfer. It's fine if you can get it.

The dry foam microspheres are collected and packaged before being subjected to any other handling. Cooling is generally preferred. This is because the polymer is in a plastic state. However, the degree to which the bead structure is disrupted by handling is minimized. If you wish Alternatively, active cooling may be used.

The resulting microspheres with a surface-blocking liquid coating are then ground into a powder or granule material. by the completely normal procedures and equipment normally employed in such operations, dealing with It can be conveniently recovered and collected from the foam machine. surface-blocking liquid at an unusually high rate. When used in liquids, use the handling equipment normally used for such liquids. May be used.

This method produces microspheres of unique morphology. This microsphere is a surface shield. It has an adhesive surface coated with a liquid or a mixture of such a liquid and a solid material. child The surface barrier liquid or the mixture of such liquid and the solid material is formed in a substantially continuous layer. completely covers the surface. Varying the ratio of barrier coating material and microspheres This allows the thickness of the coating to be controlled.

Compared to dry foamed microspheres obtained by conventional methods, the microspheres of the present invention are often , the incidence of deformed non-spherical objects is low. A hollow structure with a continuous shape is destroyed. The level of disintegrated microspheres is not frequent and is about the same as the standard in conventional methods. It was found that it is low or even lower.

The microsphere products of the present invention can be produced very close to the foamability limit, i.e. about 0.0 Less than 3 g/cm3, often 0.02 g/cm', or 0.015 g/cm3 It can even be foamed to c++3. Higher densities are also possible.

Taking into account the barrier coating material, the composite dens ity) will naturally be somewhat higher than that. Thus, the composite density of the product is The density of the particular barrier coating material used, the amount of barrier coating material included, and the degree of foaming. Depends on. With the information and guidance provided herein, those skilled in the art will be able to Material density could be determined quickly.

Most importantly, the expanded beads of the present invention contain less than 1 percent aggregate, in many cases. It will probably contain less than the total Oll part. In the present invention, this is at least about 99 percent of the product, preferably at least about 99.9 percent of the product. This means that cents pass through 100 mesh sieves. Compared to this, the conventional method The acceptable product for conventional dry expanded beads produced by spray drying is 80 ml. 3 to IO percent remains on the sieve, only about 97 percent, often 9 Only a small amount of 0% passes through a 100 mesh sieve. in many situations , especially when the microspheres exceed about 30% by weight of the Blend, in the conventional method, Agglomerates account for well over 10 percent of the product, with an even higher proportion of agglomerates accounting for 80 percent of the product. It stays on the Metsunko sieve. In the present invention, the proportion of microspheres in the blend is 80 % by weight (99% by volume or more). can be pressed less. surface-blocking liquids or the combination of such liquids with solid materials; Such a low proportion of the mixture is highly desirable for some uses of the product.

The above is a detailed description of the invention. As special guidance to those skilled in the art, the following The specific examples are intended to provide particularly clear guidance in the practice of the invention. .

Example The invention is illustrated by the results set forth in Table 2 below. Table 2 shows microspheres and Six formulations consisting of four different surface barrier liquids were used to dry the microspheres. Describes drying and optional foaming.

In the production of composite materials reported in Table 2, microsphere wet cases of the type indicated A high shear stress agitator in which the water and the surface-blocking liquid have a heating jacket and are in communication with a vacuum source. Loaded into the machine. Mixing was started and the pressure in the vessel was reduced to approximately 250 mmHg.

The temperature was then increased to 110°C over about 10 minutes. Then at this temperature for 10 minutes I kept it. Then, gradually increase the temperature until it reaches the maximum temperature shown in Table 2 over an additional 15 minutes. and held at this temperature for 2 minutes. Mix and stop the vacuum and let the surrounding air out of the container The composite material was cooled. The obtained composite material It was tested and found to have the physical properties reported in Table 2.

As the data in Table 2 shows, a wide variety of materials, proportions and composite densities (co mposite density) is quickly obtained.

Table 11 A 66.7. 060 A 33.3 0.97 386. 088B 71 ．． 4. 050 B' 28.6 0.965 330. 070B 71.4 ．． 015 C28°6 0.965 330. 021B 83.3. 14 0 D 16°7 0.965 291. 166B 93.7. 084 D 6.3 0.965 291. 079A? 1.4. 128 D 28. 6 0.965 380. 128 notes.

Microsphere type A consists of vinylidene chloride, acrylonitrile, and divinylbenzene. A wet cake of 5 micrometer diameter unfoamed microspheres of terpolymer of about 1 With a Tg of 80°C and an unexpanded density of 1.1, fully expanded microspheres have a diameter of 50 mm. It has a density of 0.015 grams per cubic centimeter in chroma.

Microsphere type B is unfoamed microspheres of vinylidene chloride with a diameter of 5 micrometers. is a wet cake with a Tg of approximately 125°C and an unfoamed density of 1.1, and a fully foamed fine powder. The spherules have a diameter of 50 micrometers, and oi per cubic centimeter. It has a density of s grams.

Liquid type A is a microcrystalline wax with a melting point of 120°C and is solid at room temperature. It is.

Liquid type B is dioctyl phthalate.

Liquid type C is Dow Corning Silicone Fluid (Dot CorningSi It is DC-200.

Liquid type D is silicone wetting agent P^-57.

Density is Durham per cubic centimeter.

The operating temperature is expressed in degrees Fahrenheit.

Claims (9)

[Claims] 1. Next step: A. First, expandable thermoplastic resin microspheres and a boiling point higher than the boiling point of the thermoplastic resin. or a mixture of such a liquid and a solid material. B. The resulting mixture is treated with sufficient heat to disrupt or prevent agglomeration of the microspheres. substantially all of the water is removed from the microspheres while stirring at high shear stress. heating for a time and at a temperature sufficient to C. with an adhesive coating of said surface barrier liquid or a mixture of such a liquid and a solid material. microsphere composite material (composite m) containing substantially no aggregates. icrospheres). having an adhesive coating of a surface-blocking liquid or a mixture of such a liquid and a solid material; A method for producing microspheres that do not contain aggregates. 2. The liquid may be a plasticizer, an oligomer, a prepolymer, a low molecular weight polymer, or an extender. , diluents, nonaqueous solvents, wetting agents, and mixtures thereof. 2. The method of claim 1. 3. the liquid is added in an amount sufficient to form a floc of the microspheres; The method of claim 1, characterized in that: 4. characterized in that the mixture is heated to a temperature sufficient to foam the microspheres. The method of claim 1. 5. Claim characterized in that said mixture is heated at a reduced pressure that facilitates water removal. Method of item 1. 6. the microspheres as a wet cake containing about 25 to 50 weight percent water; 2. The method of claim 1, wherein: 7. The liquid is a component of a polymerization reaction or a crosslinking reaction, and the reaction is syntactic. 3. A method according to claim 2, characterized in that it is carried out for the formation of polymeric foam. 8. The liquid is a plasticizer and the composite is a plasticizer. 3. A method according to claim 2, characterized in that it is incorporated into Chisol. 9. A surface blocking liquid comprising a product produced by the method according to any one of claims 1 to 8. microspheres with adhesive coatings of bodies or mixtures of such liquid and solid materials.