Patent Description:
<CIT>") provides a description of preexisting knowledge in the formation of gypsum wallboard using foaming agents. Other patent documents providing background in this area are <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>. <CIT> relates to a foaming agent, particularly one having a greater capacity for producing foam, and its use in making gypsum products. <CIT> relates to the manufacture of gypsum wallboard and to an improved surfactant composition for generating foam used in the process of making gypsum wallboard.

A new surfactant composition is provided comprising:.

in which M<NUM>, M<NUM>, and M<NUM> are independently selected, wherein "by total surfactant weight" means that these proportions only reflect the amount of these particular active surfactants, not including any amount of water, gypsum, or unspecified ingredients present in the surfactants as supplied or as formulated.

A gypsum board is disclosed comprising a core and facing sheets, the core comprising the gypsum slurry described above. The core has multiple foam voids, which are also sometimes referred to as bubbles, with the same meaning. The foam voids in the core have a greater median diameter than the foam voids in a corresponding core made under the same conditions except that all or substantially all of the R<NUM> moieties of the surfactant are replaced by R<NUM> moieties having the same number of carbon atoms.

A method of controlling the median foam void diameter in a gypsum board is disclosed. This method is carried out as follows.

A first foam water composition is provided comprising <NUM> to <NUM> wt. % active weight of an alkyl sulfate surfactant. The alkyl sulfate surfactant of the first foam water composition comprises a linear alkyl sulfate surfactant as described above. The alkyl sulfate surfactant of the first foam water composition optionally comprises a branched alkyl sulfate surfactant as described above. The weight ratio, A, of the branched alkyl sulfate surfactant to the linear alkyl sulfate surfactant of the first foam water composition is from <NUM> :<NUM> to <NUM> : <NUM>.

A second foam water composition is also provided comprising <NUM> to <NUM> wt. % active weight of an alkyl sulfate surfactant. The alkyl sulfate surfactant of the second source of foam water comprises a branched alkyl sulfate surfactant as described above. The alkyl sulfate surfactant of the second source of foam water optionally comprises a linear alkyl sulfate surfactant as described above. The weight ratio B of the branched alkyl sulfate surfactant to the linear alkyl sulfate surfactant in the second foam water composition is greater than the weight ratio A.

A gypsum slurry is formed by combining the first foam water composition (in the form of foam), the second foam water composition (in the form of foam), and stucco. The proportions of the first and second foam water compositions are selected to provide the desired median foam void diameter.

A method is disclosed of changing the median foam void diameter in a gypsum board while forming the board. The method is carried out as follows. First and second foam water compositions as described above are provided. A gypsum slurry is formed by combining a foam of the first foam water composition, a foam of the second foam water composition and stucco. While the gypsum slurry is formed, the proportions of the first and second foam water compositions are changed to change the median foam void diameter of the gypsum slurry.

Still other aspects and variations are also provided, as will be evident to a person of ordinary skill in the gypsum wallboard manufacturing art, after considering this specification and the other knowledge possessed by such a person.

The following reference characters are used in the FIGURES:.

The surfactant compositions claimed herein comprise surfactants, water, and optionally other ingredients. The proportions in the surfactant composition are from <NUM> to <NUM> wt. % by total surfactant weight, of the branched alkyl sulfate; from <NUM> to <NUM> wt. % by total surfactant weight of the linear alkyl sulfate; and from <NUM> to <NUM> wt. % by total surfactant weight of the alkyl ether sulfate. "By total surfactant weight" means that these proportions only reflect the amount of these particular active surfactants, not including any amount of water, gypsum, or unspecified ingredients present in the surfactants as supplied or as formulated.

The branched alkyl sulfate has the structure:.

in which R<NUM> is branched alkyl having from <NUM> to <NUM> carbon atoms and M<NUM> is a cation. Alternatively in any embodiment, R<NUM> has at least <NUM> carbon atoms, alternatively at least <NUM> carbon atoms, alternatively at least <NUM> carbon atoms. Alternatively in any embodiment, R<NUM> has at most <NUM> carbon atoms, alternatively at most <NUM> carbon atoms, alternatively at most <NUM> carbon atoms.

Broadly speaking, any branching of R<NUM> is contemplated.

Some non-limiting examples of <NUM>-carbon branched alkyl sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion (an "alkyl sulfate anion" is defined as R<NUM>-OSO<NUM> -); ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl sulfate anion; n-butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; or n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion.

Some non-limiting examples of <NUM>-carbon branched alkyl sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl sulfate anion; ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; n-butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion, or any isomer of hexyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion.

Some non-limiting examples of <NUM>-carbon branched alkyl sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl sulfate anion; ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; n-butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; any isomer of hexyl branching at the <NUM>-position or <NUM> position of a <NUM>-carbon-long alkyl sulfate anion; or any isomer of heptyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion.

Some non-limiting examples of <NUM>-carbon branched alkyl sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl sulfate anion; n-butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; any isomer of hexyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; any isomer of heptyl branching at the <NUM>-position or <NUM> position of a <NUM>-carbon-long alkyl sulfate anion; or any isomer of octyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion.

Some non-limiting examples of <NUM>-carbon branched alkyl sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl sulfate anion; ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl sulfate anion; n-butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl sulfate anion; n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; any isomer of hexyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; any isomer of heptyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion; any isomer of octyl branching at the <NUM>-position or <NUM> position of a <NUM>-carbon-long alkyl sulfate anion; or any isomer of nonyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl sulfate anion.

Alkyl sulfate moieties having more than one alkyl branch, of the same type or different types, are also contemplated.

Mixtures of two or more different types of branched alkyl moieties as exemplified here are also contemplated.

M<NUM> is a cation. Any suitable cation may be used, including but not limited to calcium, sodium, ammonium, or any combination of two or more of these.

The linear alkyl sulfate has the structure:.

in which R<NUM> is linear alkyl having from <NUM> to <NUM> carbon atoms and M<NUM> is a cation.

Alternatively in any embodiment, R<NUM> has at least <NUM> carbon atoms, alternatively at least <NUM> carbon atoms, alternatively at least <NUM> carbon atoms. Alternatively in any embodiment, R<NUM> has at most <NUM> carbon atoms, alternatively at most <NUM> carbon atoms, alternatively at most <NUM> carbon atoms. Some contemplated examples of R<NUM> include n-octyl, n-nonyl, n-decyl, n-undecyl, lauryl, or combinations of two or more of these. Mixtures of two or more different types of linear alkyl moieties as exemplified here are also contemplated.

M<NUM> can be any suitable cation, including but not limited to calcium, sodium, ammonium, or any combination of two or more of these.

Optionally in any embodiment, the surfactant composition comprises a weight ratio of.

R<NUM>-OSO<NUM>- +M<NUM> : R<NUM>-OSO<NUM>- +M<NUM>.

of from at least <NUM> : <NUM> to at most <NUM> : <NUM>. Alternatively in any embodiment, the weight ratio is at most <NUM> : <NUM>, alternatively at most <NUM> : <NUM>, alternatively at most <NUM> : <NUM>, alternatively at most <NUM> : <NUM>. Alternatively in any embodiment, the weight ratio is at least <NUM> : <NUM>, alternatively at least <NUM> : <NUM>, alternatively at least <NUM> : <NUM>.

The alkyl ether sulfate has the structure:.

R<NUM>-(OCH<NUM>CH<NUM>)yOSO<NUM>- +M<NUM>.

in which R<NUM> is branched alkyl or linear alkyl or a combination thereof having from <NUM> to <NUM> carbon atoms, y has an average value from <NUM> to <NUM>, and M<NUM> is a cation.

Alternatively in any embodiment, R<NUM> has at least <NUM> carbon atoms, alternatively at least <NUM> carbon atoms, alternatively at least <NUM> carbon atoms, alternatively at least <NUM> carbon atoms. Alternatively in any embodiment, R<NUM> has at most <NUM> carbon atoms, alternatively at most <NUM> carbon atoms, alternatively at most <NUM> carbon atoms, alternatively at most <NUM> carbon atoms.

M<NUM>, M<NUM>, and M<NUM> are independently selected, meaning any of them can be the same as or different from either or both of the others. Optionally in any embodiment, M<NUM>, M<NUM>, and M<NUM> can each be ammonium (NH<NUM>+). Optionally in any embodiment, M<NUM>, M<NUM>, and M<NUM> can each be sodium (Na+).

Alternatively in any embodiment M<NUM> is sodium, M<NUM> is sodium, and M<NUM> is ammonium.

Alternatively in any embodiment M<NUM> is sodium, M<NUM> is ammonium, and M<NUM> is sodium.

Alternatively in any embodiment M<NUM> is sodium, M<NUM> is ammonium, and M<NUM> is ammonium.

Alternatively in any embodiment M<NUM> is ammonium, M<NUM> is sodium, and M<NUM> is sodium.

Alternatively in any embodiment M<NUM> is ammonium, M<NUM> is sodium, and M<NUM> is ammonium.

Alternatively in any embodiment M<NUM> is ammonium, M<NUM> is ammonium, and M<NUM> is sodium.

Some non-limiting examples of <NUM>-carbon branched alkyl ether sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion (note that the carbons in the ether moieties do not count in determination of the number of carbons in the alkyl ether sulfate anion for any of these species); ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; n-butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; or n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion.

Some non-limiting examples of <NUM>-carbon branched alkyl ether sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; n-butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion, or any isomer of hexyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion.

Some non-limiting examples of <NUM>-carbon branched alkyl ether sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; n-butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; any isomer of hexyl branching at the <NUM>-position or <NUM> position of a <NUM>-carbon-long alkyl ether sulfate anion; or any isomer of heptyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion.

Some non-limiting examples of <NUM>-carbon branched alkyl ether sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; n-butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; any isomer of hexyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; any isomer of heptyl branching at the <NUM>-position or <NUM> position of a <NUM>-carbon-long alkyl ether sulfate anion; or any isomer of octyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion.

Some non-limiting examples of <NUM>-carbon branched alkyl ether sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; n-butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; any isomer of hexyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; any isomer of heptyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; any isomer of octyl branching at the <NUM>-position or <NUM> position of a <NUM>-carbon-long alkyl ether sulfate anion; or any isomer of nonyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion.

Some non-limiting examples of <NUM>-carbon branched alkyl ether sulfates include methyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; ethyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; n-propyl or isopropyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; butyl, i-butyl, t-butyl, or s-butyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; n-pentyl, i-pentyl, or neopentyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of an <NUM>-carbon-long alkyl ether sulfate anion; any isomer of hexyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; any isomer of heptyl branching at the <NUM>-position, <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; any isomer of octyl branching at the <NUM>-position, <NUM>-position, or <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion; any isomer of nonyl branching at the <NUM>-position or <NUM> position of a <NUM>-carbon-long alkyl ether sulfate anion; or any isomer of decyl branching at the <NUM>-position of a <NUM>-carbon-long alkyl ether sulfate anion.

Branched alkyl ether sulfates having more than one alkyl branch, of the same type or different types, are also contemplated. R<NUM> can also be linear alkyl having from <NUM> to <NUM> carbon atoms, specifically n-octyl, n-nonyl, n-decyl, n-undecyl, lauryl, or tridecyl.

Mixtures of two or more different types of branched and/or linear alkyl moieties as exemplified here are also contemplated. Alternatively in any embodiment, y has an average value from <NUM> to <NUM>.

A new gypsum slurry made by combining stucco, water, and a surfactant comprising any embodiment of the surfactant composition described above is contemplated. "Gypsum" technically refers to the hydrated mineral that can either be mined or produced by combining calcined gypsum - stucco - with water. Since the present compositions contain water, the mineral ingredient is specified here as gypsum, even though, if still not fully cured, some of this mineral persists as stucco. The range of proportions of gypsum is well known to those skilled in the art. For example, the present working examples provide useful proportions of stucco, water, foaming surfactant, and optionally other ingredients. A person of ordinary skill can vary and adapt these proportions and ingredients to particular processing conditions and desired compositions.

Various optional ingredients can be employed in the present gypsum slurries. Some examples of such optional ingredients, including many mentioned in paragraphs [<NUM>]-[<NUM>] of Bruce et al. are slurry set retarders or accelerators (such as finely ground gypsum and/or potassium sulfate), ball mill accelerators (for example containing starch or dextrose), water-reducing agents, dispersants, moisture-resistant agents, fire-retardant agents, paper fiber and/or chopped glass fibers, boric acid, or other ingredients. Among the effects that these additives are known to achieve are: a reduction in the amount of water required to produce a workable gypsum board core slurry; a reduced slurry viscosity; the retardation of the onset of setting of the slurry to a solid gypsum board core until after the fully formulated foamed gypsum board core has been formed into its final width; the acceleration of the setting of the calcined gypsum slurry on the setting belt; an increased resistance to product over-drying during manufacture; an increased resistance of the final product to moisture and fire; and an increased resistance to damage during shipping, handling and the installation of the manufactured gypsum board.

A new gypsum board <NUM> is contemplated comprising a foamed gypsum core <NUM> and facing sheets <NUM> and <NUM> as shown in <FIG>. The core <NUM> comprises gypsum plus any surfactant composition described above. The core <NUM> has multiple foam voids. The foam voids in the core have a greater median diameter than the foam voids in a corresponding core in which all or substantially all of the R<NUM> moieties of the surfactant are replaced by R<NUM> moieties having the same number of carbon atoms. An illustration of determining these relative median diameters is provided by comparing Examples <NUM> and <NUM>. These Examples were carried out identically, except that for Example <NUM> all of the alkyl sulfates were linear, while for Example <NUM> some of the alkyl sulfates with the same number of carbon atoms were branched, as specified in Table <NUM> (those examples in Table <NUM> which are not encompassed by the appended claims are given for comparative purposes only). Table <NUM> shows that the foam voids in the core of Example <NUM> have a greater median diameter (<NUM> micrometers) than the median diameter of the foam voids in the corresponding core of Example <NUM> (<NUM> micrometers) in which all or substantially all of the R<NUM> moieties of the surfactant (all branched C<NUM>) are replaced by R<NUM> moieties having the same number of carbon atoms (all linear C<NUM>). Thus, Example <NUM> shows how one can determine that foam voids in the core have a greater median diameter than the foam voids in a corresponding core in which all or substantially all of the R1 moieties of the surfactant are replaced by R2 moieties having the same number of carbon atoms.

A new method of controlling the median foam void diameter in a gypsum board is contemplated. This method optionally can be carried out as follows, optionally using the apparatus shown schematically in <FIG>.

A first foam water composition <NUM> is provided, for example disposed in a vessel <NUM>, comprising <NUM> to <NUM> wt. % active weight of an alkyl sulfate surfactant. The alkyl sulfate surfactant of the first foam water composition comprises a linear alkyl sulfate surfactant as described above. The first foam water composition is thus a linear-alkyl-sulfate-rich composition. The alkyl sulfate surfactant of the first foam water composition optionally comprises a branched alkyl sulfate surfactant as described above. The weight ratio, A, of the branched alkyl sulfate surfactant (if any) to the linear alkyl sulfate surfactant of the first foam water composition is from <NUM> :<NUM> to <NUM> : <NUM>. The first foam water composition can thus be a pure linear alkyl sulfate or a mixture of linear alkyl sulfate with a branched alkyl sulfate, optionally further combined with other materials. One specific example of an additional material contemplated here is an alkyl ether sulfate, which usually is combined in a minor proportion relative to the amount of alkyl sulfates.

A second foam water composition <NUM> is also provided, for example disposed in a vessel <NUM>, comprising <NUM> to <NUM> wt. % active weight of an alkyl sulfate surfactant. The alkyl sulfate surfactant of the second source of foam water comprises a branched alkyl sulfate surfactant as described above. The second foam water composition is thus a branched-alkyl-sulfate-rich composition. The alkyl sulfate surfactant of the second source of foam water optionally comprises a linear alkyl sulfate surfactant as described above. The weight ratio B of the branched alkyl sulfate surfactant to the linear alkyl sulfate surfactant in the second foam water composition is greater than the weight ratio A. One specific example of an additional material contemplated here is an alkyl ether sulfate, which usually is combined in a minor proportion relative to the amount of alkyl sulfates.

Due to the respective compositions of the first and second foam water compositions, when they are mixed, if one increases the proportion of the first foam water composition in a mixture of the two, the proportion of linear alkyl sulfate in the resulting mixture will increase, while if one increases the proportion of the second foam water composition in a mixture of the two, the proportion of branched alkyl sulfate in the resulting mixture will increase. The proportions of the first and second foam water <NUM> and <NUM> can be selected to provide the desired median foam void diameter.

It is also contemplated that the water used to make the foam water compositions may equally be added before or after the linear and branched alkyl sulfate surfactants, and/or an alkyl ether sulfate surfactant or other ingredients, are mixed. Regardless of the order of addition of the water and surfactants, this process step is regarded as combining the first and second foam water compositions.

The first foam water composition <NUM> in the tank <NUM> can be exhausted through a pipe <NUM>, metered in a specific proportion at any given time by a fluid meter <NUM>, and passed by an outlet pipe <NUM> to a mixer <NUM>. The second foam water composition <NUM> in the tank <NUM> can be exhausted through a pipe <NUM>, metered in a specific proportion at any given time by a fluid meter <NUM>, and passed to the mixer <NUM>. The mixer <NUM> mixes the first and second foam water composition to form a final foam water composition, and passes the final foam water composition via a pipe <NUM> to the foam generator <NUM>. The foam generator <NUM> employs mechanical energy, such as rotation of an impeller, to generate foam <NUM> from the foam water.

Alternatively in any embodiment, the first and second foam water compositions can be foamed independently, for example in separate foam generators, and the respective streams of foam combined either before or as the foam and stucco are mixed in the slurry mixer.

In still another embodiment, a third foam water composition can also be prepared and mixed into the gypsum slurry. The third foam water composition optionally can be combined with one or both of the first and second foam water compositions as a still composition or as separately generated foam. Alternatively, the third foam water composition can be added directly to the gypsum slurry mixer in the form of foam.

Separately, a gypsum slurry is formed by combining the foam <NUM>, stucco <NUM>, optionally gauge water <NUM>, and optionally minor proportions of other ingredients. Any method, order of steps, or equipment can be used.

Referring again to <FIG>, when forming a gypsum slurry, stucco <NUM> provided in a suitable bin <NUM> can be conveyed via a chute <NUM> by a dry material feeder <NUM>, such as a screw feeder, to a mixing vessel <NUM>. Gauge water <NUM> provided in a suitable tank <NUM> can be conveyed via a drain <NUM>, a metering feeder <NUM>, and a pipe <NUM> to the mixing vessel <NUM>, optionally an in-line or other type of continuous mixer, where the stucco <NUM> and gauge water <NUM> can be mixed to form a still (unfoamed) gypsum slurry <NUM>.

The still gypsum slurry <NUM> can leave the mixing vessel <NUM> via a pipe <NUM>, a metering feeder <NUM>, and a pipe <NUM> to a further mixing vessel <NUM>. The foam <NUM> can be conveyed via a pipe or trough <NUM>, a foam feeder <NUM>, and a pipe or trough <NUM> to the further mixing vessel <NUM>, which for example can be a pin mixer, a pinless mixer, or any other useful type of slurry mixer. The further mixing vessel <NUM> is operated to mix the foam <NUM> and the still gypsum slurry <NUM> to form a foamed gypsum slurry <NUM>.

Alternatively, the stucco <NUM>, gauge water <NUM>, and foam <NUM> could be combined in a single mixer to form a foamed gypsum slurry <NUM>.

Alternatively, the foam water <NUM> and the foam water <NUM> could be separately foamed and the two streams of foam could be mixed together either upstream of or directly with the stucco <NUM> and gauge water <NUM> in a single mixer <NUM> to form a foamed gypsum slurry <NUM>.

The foamed gypsum slurry <NUM> can leave the further mixing vessel <NUM> via a pipe or trough <NUM> and can be deposited at the deposition point <NUM> on a running lower web <NUM> of paper or another type of facing sheet. The foamed gypsum slurry can be sandwiched to form a gypsum board <NUM> by applying a running upper web <NUM> of paper or other material on the foamed gypsum slurry. The foamed gypsum slurry <NUM>, contained between its facing sheets defined by the running lower web <NUM> and running upper web <NUM>, is then cured and cut to form gypsum wallboards or another product.

The median foam void diameter in the gypsum board <NUM> is controlled by controlling the proportions of the first foam water <NUM>, which increases the proportion of linear alkyl sulfate, and the second foam water <NUM>, which increases the proportion of branched alkyl sulfate when the first and second foam waters <NUM> and <NUM> or the resulting foams are mixed. The higher the proportion of branched alkyl sulfate, the larger the median foam void diameter in the gypsum board <NUM>.

Alternatively, the apparatus and methods described in Bruce et al. can be used.

Also contemplated is a new method of changing the median foam void diameter in a gypsum board while forming the board. The method can be used, for example, to correct a deviation from the intended median foam void diameter, preferably while the board forming line remains operating to minimize or eliminate down time.

The method can be carried out as follows. First and second foam water compositions <NUM> and <NUM> and stucco <NUM> as described above are provided, again optionally including additional ingredients. A foamed gypsum slurry <NUM> is formed comprising the first foam water composition <NUM>, the second foam water composition <NUM>, and stucco <NUM> and delivered at the delivery point <NUM>. While the foamed gypsum slurry <NUM> is being formed, the proportions of the first and second foam water compositions <NUM> and <NUM> are changed to change the median foam void diameter of the gypsum slurry, and thus the median foam void diameter in the gypsum board <NUM>.

In addition to using branching to increase foam void diameter, other expedients may also be used. For example, it has been found that using more alkyl sulfate surfactant and less alkyl ether sulfate surfactant, or a less-highly-ethoxylated alkyl ether sulfate, may lead to larger median foam void diameters. Another observation is that shorter chain alkyl sulfate foamers may produce larger median foam void diameters than longer chains.

The following examples describe some of the preferred embodiments of the present technology without limiting the technology. Those examples which are not encompassed by the appended claims are given for comparative purposes only.

Some alkyl sulfate or alkyl ether sulfate foamers were provided having a single number of carbon atoms per molecule (like Example <NUM>, all C<NUM>), while other foamers were provided having a mixture of more than one number of carbon atoms per molecule (like Example <NUM>, mixture of C<NUM> and C<NUM>) and various degrees of branching. The alkyl sulfate or alkyl ether sulfate components specified as having a single number of carbon atoms per molecule were formed by synthesizing a relatively pure linear or branched primary alcohol having that number of carbon atoms per molecule, ethoxylating if appropriate, then sulfating the alcohol or its ethoxylated product, as appropriate, to produce an alkyl sulfate or alkyl ether sulfate having a single number of carbon atoms. The alkyl sulfate or alkyl ether sulfate components specified as having a mixture of components having different numbers of carbon atoms per molecule were made by blending two or more of the separately made alkyl sulfates or alkyl ether sulfates, each having a single number of carbon atoms. The alkyl sulfate and alkyl ether sulfate materials identified by trademarks were made in the usual manner.

To prepare foam water, the selected gypsum foaming surfactant (sometimes referred to as a "foamer") was combined with room temperature tap water by placing appropriate amounts of water and foamer into the metal milkshake cup of a Hamilton Beach commercial milkshake mixer to produce <NUM> of solution containing the desired amount of active foamer material (typically <NUM> wt. %, <NUM> wt. %, <NUM> wt. %, or <NUM> wt. % as reported in TABLE <NUM>). The solution in the cup was gently swirled to ensure good mixing. The resulting mixture is sometimes referred to as "foam water. " To initially generate foam, the milkshake cup was placed on the Hamilton Beach mixer and the foam water was mixed on the "high" setting (~<NUM>,<NUM> rpm) for <NUM> seconds. Separately, to prepare gauging water, a plastic beaker was charged with <NUM>. tap water, <NUM>. retarder, and <NUM> dispersant.

To prepare the dry ingredients, a Hobart commercial mixer bowl was charged with <NUM>. stucco, <NUM>. boric acid, <NUM> ball mill accelerator (BMA) containing <NUM>% dextrose, and <NUM> starch. These dry ingredients were gently stirred together with a spatula. The bowl was then set up on the Hobart mixer with a whisk attachment.

To prepare the gypsum slurry, an open-ended large plastic syringe with a capacity of <NUM> was filled with foam poured from the metal cup of the Hamilton Beach mixer. (transferring <NUM> of foam did not consume all of the foam in the metal milkshake cup. ) The <NUM> of foam was placed in the Hobart mixer bowl and then the gauging water was quickly added. The Hobart mixer was started and run on high (level <NUM>) for <NUM> seconds.

To form the slump samples, the mixed gypsum slurry made as described above was immediately poured into a slump cylinder <NUM>. long, with an inside diameter of <NUM>, supported on a flat surface. The slump cylinder was lifted away from the slump sample precisely <NUM> seconds after the start of the Hobart slurry mixer when preparing the gypsum slurry. A quarter-pound (<NUM>. ) Gillmore needle was used to measure the initial set time of the gypsum slurry, which is reported in Table <NUM>. The set time was recorded when the needle was gently placed on the surface of the slump sample and no longer made an indentation. The slump sample was allowed to harden and dry for at least <NUM> hours.

Once the slump sample was hardened, the diameter was measured and reported in Table <NUM>. The slump sample was scored and broken across its diameter to produce a cross section in the form of a broken surface. A Dino-Lite® handheld microscope camera was used to take three pictures roughly equally spaced across the diameter of the slump sample. A software program for the Dino-Lite® microscope was used to measure foam void diameters in the slump sample pictures. Approximately <NUM> foam voids were measured for each slump, with more measured for slump samples having smaller foam voids and fewer measured for slump samples having larger foam voids. The median foam void diameter was then calculated for each slump sample. The median value was selected for reporting to minimize the effect of occasional large outlier foam voids. The median foam void diameter is reported in Table <NUM>.

<NUM> of foam water was prepared as described before. The foam volume was measured by using a spatula to quickly transfer the foam from the milkshake cup to a <NUM> graduated cylinder, using a funnel with a large spout to facilitate the transfer. The foam volume was measured. The foam volume was measured twice for each sample, and the two measurements averaged to determine the foam volume reported in Table <NUM>.

Following the stated protocols, sodium alkyl sulfate foamers with the alkyl chain lengths, degree of branching, foamer proportions in wt. %, and properties indicated in TABLE <NUM> were used to make slump samples, and the data reported in Table <NUM> was measured. Except for the commercial alkyl sulfate and alkyl ether sulfate surfactants identified in Examples <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>, the samples were made by combining substantially pure single-chain-length sodium alkyl sulfate surfactants that were either essentially entirely branched or entirely linear. The branched sodium alkyl sulfate surfactants having <NUM> or more carbon atoms were methyl branched, so for example the C<NUM> linear species was sodium n-nonyl sulfate and the C<NUM> branched species was sodium <NUM>-methyl octyl <NUM>-sulfate (also known as sodium iso-nonyl sulfate). The C<NUM> branched species was sodium <NUM>-ethyl hexyl sulfate, sold by the applicant as Stepanol® EHS, and the C<NUM> linear species was sodium n-octyl sulfate, sold by the applicant as Polystep® B-<NUM>.

The data for Examples <NUM> and <NUM> of Table <NUM> did not show any significant difference in foam void diameter. The median foam void diameter of Example <NUM> (<NUM>) and the median foam void of Example <NUM> (<NUM>) differ by <NUM>. Foam void diameters that are less than <NUM> apart are regarded as essentially identical in this work.

In Table <NUM>, certain data reported in Table <NUM> is repeated, juxtaposing otherwise similar examples with differences in branching, to isolate the effect of branching on median foam void diameter. For instance, in Example <NUM> the foamer was a mixture of <NUM>% by weight of a sodium C<NUM> linear primary alkyl sulfate and <NUM>% by weight of a sodium C<NUM> linear primary alkyl sulfate, at a concentration of <NUM> wt. % of the foam water. Example <NUM> provided a median foam void diameter of <NUM> micrometers (µm). In Example <NUM>, the foamer differed from that of Example <NUM> only in that the C<NUM> component was a <NUM>% branched sodium primary alkyl sulfate. The substitution of a branched component in Example <NUM> led to an increase in median foam void diameter from <NUM> to <NUM> - an increase of <NUM>%. Yet, the foam volume changed by only <NUM>%, from <NUM> to <NUM>. The ability to change the median foam void diameter substantially, with only a small change in foam volume, provides an advantage in regulating a gypsum slurry manufacturing process, as the median foam void diameter can be adjusted by varying the degree of branching in the surfactant feed with minimal change to the volume of foam. A substantial change, particularly a decrease, in the volume of foam in a short time can lead to the formation of a large void pocket in the gypsum slurry adjacent to the facing sheets, leaving the adjacent portions of the facing sheets unsupported and vulnerable to tearing.

Referring again to Table <NUM>, a similar comparison can be made between the median foam void diameters and in some instances the foam volumes of the following pairs (and in one instance a trio) of slump samples:.

Surprisingly, the substantial increase in median foam void diameter due to branching, shown in Table <NUM>, occurs even though the foam volume changes much less, and often decreases, when increasing the proportion of branched species.

Table <NUM> also shows that as the average number of carbon atoms increases, the substitution of the branched species reduces the foam volume more.

Following the stated protocols, sodium alkyl sulfate foamers with the alkyl chain lengths, degree of branching, foamer proportions in wt. %, and properties indicated in TABLE <NUM> are used to make slump samples, and data of the types reported in TABLE <NUM> is measured. The samples are made by combining substantially pure single-chain-length sodium alkyl sulfate surfactants that are either essentially entirely branched or entirely linear. The branched sodium alkyl sulfate surfactants having <NUM> or more carbon atoms are methyl branched, so for example the C<NUM> linear species is sodium n-nonyl sulfate and the C<NUM> branched species is sodium <NUM>-methyl octyl <NUM>-sulfate (also known as sodium iso-nonyl sulfate). The C<NUM> branched species is sodium <NUM>-ethyl hexyl sulfate, sold by the applicant as Stepanol® EHS, and the C<NUM> linear species is sodium n-octyl sulfate, sold by the applicant as Polystep® B-<NUM>.

Following the stated protocols, ammonium alkyl sulfate foamers with the alkyl chain lengths, degree of branching, foamer proportions in wt. %, and properties indicated in TABLE <NUM> are used to make slump samples, and data of the types reported in TABLE <NUM> is measured. The samples are made by combining substantially pure single-chain-length ammonium alkyl sulfate surfactants that are either essentially entirely branched or entirely linear. The branched ammonium alkyl sulfate surfactants having <NUM> or more carbon atoms are methyl branched, so for example the C<NUM> linear species is ammonium n-nonyl sulfate and the C<NUM> branched species is ammonium <NUM>-methyl octyl <NUM>-sulfate (also known as ammonium iso-nonyl sulfate). The C<NUM> branched species is ammonium <NUM>-ethyl hexyl sulfate, and the C<NUM> linear species is ammonium n-octyl sulfate.

The present technology is now described in such full, clear and concise terms as to enable a person skilled in the art to which it pertains to practice the same.

Claim 1:
A surfactant composition comprising:
• from <NUM> to <NUM> wt.% by total surfactant weight of a branched alkyl sulfate having the structure:

        R<NUM>-OSO<NUM> - +M<NUM>,

in which R<NUM> is branched alkyl having from <NUM> to <NUM> carbon atoms and M<NUM> is a cation;
• from <NUM> to <NUM> wt.% by total surfactant weight of a linear alkyl sulfate having the structure:

        R<NUM>-OSO<NUM>- +M<NUM>,

in which R<NUM> is linear alkyl having from <NUM> to <NUM> carbon atoms and M<NUM> is a cation; and
• from <NUM> to <NUM> wt.% by total surfactant weight of an alkyl ether sulfate having the structure:

        R<NUM>-(OCH<NUM>CH<NUM>)yOSO<NUM>- +M<NUM>

in which R<NUM> is branched alkyl or linear alkyl or a combination thereof having from <NUM> to <NUM> carbon atoms, y has an average value from <NUM> to <NUM>, and M<NUM> is a cation; in which
• M<NUM>, M<NUM>, and M<NUM> are independently selected,
wherein "by total surfactant weight" means that these proportions only reflect the amount of these particular active surfactants, not including any amount of water, gypsum, or unspecified ingredients present in the surfactants as supplied or as formulated.