Methods for compression molding foam articles

A method for making a compression molded foam article, the method comprising:

• arranging a preform in a compression mold;
• wherein the preform comprises a polymeric foam material having a closed cell foam structure;
• wherein the preform is associated with a preform x-axis, y-axis, and z-axis such that each axis is perpendicular to the other two;
• wherein the preform has a preform longitudinal dimension parallel to the preform y-axis of a preform x-y plane;
• wherein the preform z-axis is parallel to the direction of compression applied to the compression mold;
• wherein the preform has a preform height that is a dimension parallel to the preform z-axis;
• wherein the preform has an initial preform height equal to the preform height prior to compression molding;
• wherein the compression mold comprises a mold cavity;
• and wherein the mold cavity is associated with a mold cavity x-axis, y-axis, and z-axis such that each axis is perpendicular to the other two;
• wherein the mold cavity has a mold cavity longitudinal dimension parallel to the mold cavity y-axis of a mold cavity x-y plane;
• wherein the mold cavity z-axis is parallel to a direction of compression applied to the compression mold;
• wherein the mold cavity has a mold cavity height that is a dimension parallel to the preform z-axis when the mold is closed;
• wherein the arranging comprises aligning the preform x-axis, y-axis, and z-axis with the mold cavity x-axis, y-axis, and z-axis;
• and
• wherein the initial preform height is from 1.1- to 5-fold greater than the mold cavity height;
• closing the compression mold and compressing the preform into a closed mold cavity;
• applying heat, pressure, or a combination of both to the closed mold cavity for a duration of time to:
• (a) alter at least one preform dimension along the preform x-axis, y-axis, and z-axis;
• and
• (b) alter the closed cell foam structure to a closed cell foam structure having a greater proportion of anisotropic cell shapes;
• forming the compression molded foam article;
• opening the compression mold after the at least one preform dimension in the preform x-axis, y-axis, and z-axis and the closed cell foam structure are altered;
• removing the compression molded foam article from the compression mold;
• and
• wherein the compression molded foam article retains dimensions of the closed mold cavity within plus or minus 50 percent;
• and
• wherein the compression molded foam article has the closed cell foam structure having a greater proportion of closed cells with the anisotropic cell shapes as compared to the preform, or having substantially the same proportion of closed cells with the anisotropic cell shapes as compared to the preform, where an average aspect ratio of the proportion of the closed cells with the anisotropic cell shapes is greater as compared to the preform, or both the proportion and the aspect ratio of closed cells with the anisotropic cell shapes are greater in the closed cell foam structure of the compression molded foam article as compared to the closed cell foam structure of the preform;
• characterized in that, either:
• (A) the preform has a preform area comprising an area of the preform x-y plane and the preform has an initial preform area that is the preform area prior to compression molding;
• and
• the mold cavity has a mold cavity area corresponding to an area of a mold cavity bottom and the mold cavity bottom is a mold cavity x-y plane opposite a mold cavity opening;
• wherein the initial preform area is less than about 75 percent of the mold cavity area,
• or
• (B) the preform has a plurality of initial preform widths;
• wherein each initial preform width of the plurality of initial preform widths is designated as IPWi, wherein i is an integer having a value of 1 to 100;
• and each IPWi has a dimension parallel to the preform x-axis of the preform x-y plane at a position, Yi, along the preform longitudinal dimension prior to compression molding;
• the mold cavity has a plurality of mold cavity widths;
• wherein each mold cavity width of the plurality of mold cavity widths is designated as CWj, wherein j is an integer having a value of 1 to 100;
• wherein each CWj has a dimension parallel to the mold cavity x-axis of the mold cavity x-y plane of the preform at a position, Pj, along the mold cavity longitudinal dimension;
• wherein each Pi is associated with a corresponding position of the preform longitudinal dimension when the preform y-axis and the mold cavity y-axis are aligned;
• and the preform and the mold cavity are associated with a plurality of mold gaps;
• wherein each mold gap of the plurality of mold gaps is designated as MGk, wherein k is an integer having a value of 1 to 100;
• wherein each MGk is obtained from the following equation:
• M
• ⁢
• G
• k
• =
• CW
• j
• -
• IPW
• i
• CW
• j
• and wherein each mold gap is independently from about 0.200 to about 0.7,
• or
• (C) the preform has a preform volume, wherein the preform has an initial preform volume that is the preform volume prior to compression molding;
• and the mold cavity has a mold cavity volume associated with the mold when it is closed;
• wherein less than about 80 percent of the mold cavity volume is occupied by the preform;
• and at least 50 percent of the initial preform volume is positioned outside the mold cavity.

A compression molded foam article which is a cushioning element that is a midsole or midsole component for an article of footwear comprising:

• an elastomeric material having a closed cell foam structure comprising a plurality of cells having an anisotropic cell shape;
• wherein the foam cushioning element comprises a first axis (z), a second axis (y) and a third axis (x);
• wherein the first axis (z) is perpendicular to the second axis (y) and the third axis (x);
• wherein the second axis (y) and the third axis (x) are each perpendicular to each other;
• wherein the second axis (y) and the third axis (x) define a plane (x-y) parallel to a major surface of the foam article;
• wherein the plurality of cells are aligned in an orientation along the second axis (y) within a range of a solid angle of plus or minus 20 degrees;
• and wherein a physical property determined along the first axis (z) is different from the physical property determined along the second axis (y), the third axis (x), or both the second (y) and third axis (x).