The Dow Chemical Company

Donald L Tomkinson

Wilhelm E Walles

Trevor D Williamson

David R Near

Robert O Mass

Wilhem E Walles

A controlled release composition for use with liquid acids, and a method of preparation is disclosed. The composition comprises (1) a porous matrix comprising and substantially inert to an absorbed acid; (2) a midlayer surrounding the matrix, this midlayer consisting essentially of a salt of the absorbed acid; and (3) a membrane surrounding the matrix, the membrane being exterior of the midlayer, the membrane further being substantially inert to the midlayer and permeable to a selected environment, the thickness and permeability of the membrane comprising means for controlling diffusion of the environment therethrough. The midlayer can be applied as a coating to the acid-bearing matrix, or it can be evolved by exposing the acid-bearing matrix to a base such as ammonia gas or a solid metal oxide for a time sufficient to allow reaction of a proportion of the acid at or near the surface of the matrix with the base to form a layer of the corresponding salt.

Controlled-release compositions for acids

The present invention provides an apparatus for generating a reagent of sulfur trioxide in a carrier which includes a reagent generator. The reagent generator has associated therewith means for introducing a source of sulfur trioxide into the reagent generator, means for introducing a carrier such as a liquid halocarbon or an inert gas into the reagent generator, and means for introducing oleum into the reagent generator. The reagent generator also includes means for contacting the sulfur trioxide, carrier, and oleum to provide a reagent of sulfur trioxide in the carrier. Additionally, the system includes means for removing oleum from the reagent generator, as well as means for removing the reagent from the reagent generator. In a preferred embodiment, the system for generating the reagent also includes, in conjunction with the reagent generator, a treatment chamber for the surface treatment of polymer resins including medical products which have polymeric resin material on exposed surfaces thereof.

Apparatus for the generation of sulfur trioxide reagent and sulfonation

The present invention provides a process for generating a reagent of sulfur trioxide in a carrier. A source of sulfur trioxide, a carrier, and oleum are introduced into a reagent generator. The sulfur trioxide, carrier, and oleum are then contacted to provide a reagent of sulfur trioxide in the carrier. Separate oleum and sulfur trioxide in carrier phases are formed, and oleum is removed from the reagent generator. The sulfur trioxide in carrier reagent is then ready to be used, preferably in a process to treat the surfaces of polymeric resin material such as medical devices fabricated from a variety of polymeric resins. The carrier may be either a liquid halocarbon solution or an inert gas.

Process for the generation of sulfur trioxide reagent and sulfonation of

An in-mold sulfonation system for sulfonating the surface of plastic articles such as plastic containers during molding. Sulfur trioxide is introduced into a pre-mold chamber, converted to a relatively high pressure gaseous sulfur trioxide, and then injected into a mold such as a blow mold immediately before or immediately following full expansion of the formed plastic article in the mold cavity. Neutralization with a gaseous neutralizing agent follows. By controlling the timing and temperature of the in-mold sulfonation step it is possible to produce a plastic article having an effective barrier layer but containing a minimum of undesirable rinseable salts.

Mold sulfonation system

Novel controlled-release compositions are disclosed. These compositions comprise: (1) an agent suitable for use in a selected environment; and (2) a membrane surrounding this agent. The membrane is substantially inert to the agent and permeable to the environment, its thickness and permeability comprising a means for controlling diffusion of the environment therethrough. The membrane thickness is substantially uniform due to the presence of a quantity of submicron particles therein, these particles being substantially inert to the membrane and the agent. The membrane comprising the submicron particles is capable of releasing the agent to the selected environment at a predetermined time by a variety of mechanisms. The release mechanisms that may be selected for use with a composition will depend in part on the choices of agent, membrane, and submicron particle materials, as well as on the choice of environment into which the composition is to be introduced.

Controlled-release composition having a membrane comprising submicron

Control release capsules comprising a breaker contained within a enclosure member are employed to break fracturing fluids. The enclosure member is permeable to at least one fluid in the subterranean formation or injected with the capsules such that upon sufficient exposure to the fluid, the capsules rupture, thereby releasing the breaker to the formation. In such manner, the release of the breaker can be conducted in a controlled manner. In addition, the entire amount of breaker introduced into the formation is released.

Method for treating subterranean formations

Reliable continual preparation of polymers is obtained using a tubular reactor by intermittently feeding monomer, permitting substantial polymerization, adding additional monomer to displace a portion of the polymer formed and repeating the foregoing cycle. Plugging of the reactor is avoided.

Growing community of inventors

Auburn, MI, United States of America

Donald L Tomkinson