CA1055965A - Thermally crystallizable glass - Google Patents

Abstract

THERMALLY CRYSTALLIZABLE GLASSES POSSESSING
PRECISION CONTROLLED CRYSTALLIZATION AND FLOW
PROPERTIES AND PROCESS OF PRODUCING SAME

ABSTRACT OF THE DISCLOSURE
A thermally crystallizable glass of predominantly lead-zinc borate composition is disclosed which is composes of a homogeneous admixture of finely comminuted particles of thermally crystallizable glass and essentially fully crystallized glass particles in a ratio of about 1-10, or more preferably 2-7, parts by weight of crystallized glass particles to one million parts by weight of uncrystallized glass particles and which, in its finely comminuted state, possesses an overall particles which are essentially entirely of -100 U.S. Series Sieve screen size and such that between about 65-78 weight percent of such particles are of -325 U.S. Series Sieve screen size. The thermally crystallizable glass composition is produced by a process involving the steps of providing a quantity of uncrystallized chips of crystallizable glass having a thickness of about 20-25 mils, and a quantity of essentially fully crystallized glass having a particle size ranging between about -20 and +80 U.S. Series Sieve screen size; reducing the particle size of the uncrystallized glass and fully crystallized to a particle size range wherein essentially all of the uncrystallized glass and fully crystallized glass particles are less than 100 U.S. Series Sieve screen size and wherein between about 65-78 percent by weight of the uncrystallized glass and full crystallized glass particles are less than 325 U.S.
Series Sieve screen size; blending the fully crystallized glass particles together with the uncrystallized class particles in a ratio of between about 100-225 parts by weight of crystallized glass particles to one million parts by weight of uncrystallized glass particles to produce a uniform "master blend" of finely comminuted, crystallized and uncrystallized glass particles.
The "master" blend is then used for blending with uncrystallized particles of thermally crystallizable glass having a composition similar to that of the "master blend" and having s particle size such that essentially all of the uncrystallized particles are of -100 U.S. Series Sieve screen size and such that between about 65-78 percent by weight are of -325 U.S. Series Sieve screen size; the ratio of "master blend" to uncrystallized glass particles being selected to produce a homogeneous resulting blend or "product blend" composed of from about 1-10, or more preferably 2-7, parts of fully crystallized glass particles to each one million parts of uncrystallized glass particles.

Claims (5)

The embodiments of the invention in which an exclusive property of privilege is claimed are defined as follows:

1. A thermally crystallizable glass primarily composed of a uniform blend of finely comminuted, crystallized and uncrystallized particles of thermally crystallizable glass, said crystallized particles and said uncrystallized particles being present in said glass in a relative ratio of between 100-225 parts by weight of crystallized particles for each million parts by weight of uncrystallized particles.

2. A thermally crystallizable glass composition as defined in claim 1 consisting essentially of a uniform blend of finely comminuted particles of crystallized glass and uncrystallized particles of thermally crystallizable glass, said crystallizable glass and said crystallized glass each consisting essentially of the following constituents within the following indicated ranges of percents by weight:
Constituent Oxides Percent by Weight PbO 70 - 82 ZnO 7 - 20 SiO2 1 - 10 Al2O3 0 - 5 Other compatible glass forming constituents;
with no single constituent exceeding ten (10) percent by weight 0 - 17

3. A method of tailoring the crystallization rate and flow rate characteristics of a thermally crystallizable glass comprising the steps of:
providing a quantity of uncrystallized, thermally crystallizable glass;
comminuting said thermally crystallizable glass into particles having a particle size distribution such that essentially all of the particles possess a particle size of -100 mesh screen size and such that between about 65-78 weight percent of the particles possess a particle size of -325 mesh screen size;
providing a quantity of thermally crystallized glass;
comminuting said thermally crystallized glass into particles having a particle size distribution such that essentially all of the particles possess a particle size of -100 mesh screen size and such that between about 65-78 weight percent of the particles possess a particle size of -325 mesh screen size;
uniformly blending said particles of crystallized glass and said particles of uncrystallized, thermally crystallizable glass together into a master blend in a ratio of between 100-225 parts by weight of particles of crystallized glass to each one million parts by weight of particles of uncrystallized glass.

4. The method, as defined in claim 3 wherein said step of providing a quantity of uncrystallized, thermally crystallizable glass includes providing same as a lead-zinc borate glass.

5. The method, as defined in claim 3 including the further steps of:
providing a second quantity of particles of uncrystallized, thermally crystallizable glass having a particle size distribution such that essentially all of the particles possess a particle size of -100 mesh screen size and such that between about 65-78 weight percent of the particles possess a particle size of -325 mesh screen size;
uniformly blending said master blend with said second quantity of particles of uncrystallized, thermally crystallizable glass in an amount productive of a product blend having a ratio of 1-10 parts by weight of particles of crystallized glass to each one million parts by weight of particles of uncrystallized glass.